DEFI Explained Simply: How It Works

Decentralized finance, or DeFi, refers to financial applications built with blockchain-based software. To understand how one works, look beyond its user interface: identify the software that applies the application’s rules, the blockchain that records relevant state, and the services or components that connect users to that system. These pieces can be distributed differently, so the label “DeFi” does not, by itself, establish how decentralized or independently operable a particular application is.

This explainer maps DeFi’s components, a common transaction flow, and the boundaries between protocol behavior and surrounding services. It focuses on system mechanics, not on choosing a product or predicting financial outcomes.

What DEFI Explained Simply means

A useful starting point is to treat DeFi as a system rather than a single product. In the reference model described in Bank for International Settlements (BIS) Working Paper 1066, a DeFi application can be analyzed through three layers: settlement, application, and interface. Each layer has distinct technical dependencies, though a particular system may distribute or combine them differently. (This is a reference model, not a claim that every DeFi application has three separate components.)

  • Settlement layer: The blockchain infrastructure on which relevant transactions are recorded and settled.
  • Application layer: Software, often including smart contracts, that implements application-specific operations and rules.
  • Interface layer: The software or service through which a user views information and submits an action.

The distinction helps explain what a user may mean by “using DeFi.” A person might interact through an interface, while the application logic executes elsewhere and transaction state is recorded on a blockchain. Those layers may depend on different operators, software, or infrastructure. The exact arrangement depends on the system being examined.

A decentralized exchange (DEX) illustrates one possible design. In the public permissionless DEX model considered by BIS, users can retain control of assets while trades execute or settle through smart contracts on a blockchain. “Can retain” describes that model; it is not a guarantee about every DEX, every asset, or every step of a particular transaction.

Core components of DEFI Explained Simply

A technical review can separate the system into components and ask what each one does:

  1. User and wallet. A user initiates an action through software that can submit a transaction. The particular custody and key-control arrangements must be checked for the product and workflow; the term DeFi alone does not specify them.
  2. Interface. A website, application, or other access point may display information and prepare or relay a transaction. An interface is not necessarily the application logic itself. DEX designs can still depend on interfaces, relayers, administrators, or off-chain order components.
  3. Application logic. Smart contracts can implement operations. In an automated market maker (AMM) DEX model, smart contracts and liquidity pools implement trading. Other DEX designs—including order-book, auction, intent-based, cross-chain, and hybrid designs—can use different execution paths.
  4. Blockchain settlement. In the AMM DEX model described by BIS, a transaction is settled when it is included in a blockchain block. That statement concerns this model; it should not be generalized into a claim that all DeFi actions share the same execution or settlement path.
  5. External dependencies. A system’s layers may rely on services or components beyond the contracts and blockchain. The BIS layer model allows for distinct dependencies, while the DEX comparison specifically notes possible reliance on interfaces, relayers, administrators, or off-chain order components. Which dependencies matter is system-specific.

This component view prevents a common category error: seeing an on-chain contract does not establish that every part of the user experience, order process, or system operation is on-chain. Conversely, an interface dependency does not by itself explain how the underlying contracts or settlement behave. Each part needs its own evidence.

How DEFI Explained Simply works

An AMM-based DEX provides a concrete, bounded example of the flow. It is one DEX model, not a universal description of DeFi.

  1. The user prepares an action. Through an interface, a user can select a trading action and prepare a transaction. The interface may be one of the dependencies in the process; its role should be distinguished from the contract’s role.
  2. The transaction is submitted. The prepared transaction is sent for processing on the relevant blockchain. The source claims describe the AMM model’s contract and settlement mechanics, but do not establish one universal submission route for all applications.
  3. The application logic processes the trade. In this AMM model, smart contracts and liquidity pools implement trading. The exact rules and transaction details belong to the particular implementation; they should not be inferred from the general label “AMM.”
  4. The blockchain records settlement. The transaction is settled when it is included in a blockchain block, according to the BIS description of the AMM DEX model.
  5. The user checks the result and dependencies. A system review should distinguish the application’s documented behavior from the interface and any other components needed to prepare, relay, or interpret an action. The cited claims do not establish that every system will present, process, or recover from an action in the same way.

For a different design, the sequence may differ. An order-book, auction, intent-based, cross-chain, or hybrid DEX can use another execution path. A sound explanation therefore names the design being described before tracing steps, rather than treating one example as a template for every DeFi application.

Trust and control boundaries

DeFi’s name is not evidence that control is evenly distributed. The BIS crypto-ecosystem report notes that crypto and DeFi systems can exhibit substantial de facto centralization, even when their stated architecture or ethos emphasizes decentralization. The degree and location of concentration must be assessed for a specific network, asset, application, and time window.

For a particular system, separate at least four questions:

  • Who controls the assets at each step? The public permissionless DEX model discussed by BIS can allow users to retain control while trades execute or settle through contracts. DEX designs differ, so confirm the actual custody and authorization arrangement rather than assuming it from the category name.
  • Where does execution occur? Determine which operations are performed by contracts, which depend on off-chain components, and how the blockchain records the relevant transaction. The AMM flow is only one model.
  • Which components are operationally necessary? An interface, relayer, administrator, or off-chain order component may be a dependency in a DEX design. Identify whether and how the specific system depends on such components; do not assume they are present or absent.
  • Where is control concentrated? A system’s stated design and its actual concentration are different questions. The relevant assessment is specific to the network, asset, application, and time window—not a permanent conclusion about DeFi as a whole.

These distinctions describe possible control boundaries; they do not establish a security outcome. A contract-based step, a user-controlled asset, or a decentralized design label should not be treated as proof that all operational dependencies are absent.

Limitations and failure modes

The available evidence supports a bounded architectural account, not a guarantee that a particular application will work as intended. The layer model says dependencies differ, and the DEX research identifies design variation and possible off-chain or service dependencies. Those facts make implementation-specific verification necessary; they do not substantiate a universal list of incidents or quantify the likelihood of failure.

A further operational consideration is liquidity. The Principles for Financial Market Infrastructures (PFMI) state that payment or settlement infrastructure should manage sufficient liquid resources in relevant currencies to meet settlement obligations under normal and stressed conditions. This is an operational analogy when considering crypto payment infrastructure: the PFMI standard applies to designated financial market infrastructures, not every crypto product. It should not be presented as a rule that automatically governs every DeFi application.

More generally, the system boundary matters when interpreting a claim. A description of a smart contract does not, by itself, document an interface’s behavior or every off-chain component. A description of one DEX execution model does not establish how an order-book, auction, intent-based, cross-chain, or hybrid design works. And a claim that a user can retain control of assets in a public permissionless DEX model does not establish the custody arrangement for every product or transaction.

What teams should verify

Builders, operators, institutions, and technical decision-makers can use the following evidence-led checklist to map a DeFi system without assuming that all implementations are alike:

  1. Name the system and its design. Identify the specific application and whether the relevant example is an AMM, order-book, auction, intent-based, cross-chain, or hybrid DEX design. Do not apply the AMM flow to a different model without supporting documentation.
  2. Map the layers. Record how settlement, application, and interface functions are implemented. Note where layers are combined or distributed, consistent with the BIS reference model’s condition that systems may arrange them differently.
  3. Trace one action. Document how a user action is prepared, which component handles the application logic, and how the relevant transaction is recorded or settled. Mark any step that depends on the specific implementation rather than general DEX mechanics.
  4. Check control boundaries. Verify the actual asset-control and authorization arrangement for the workflow. Treat the BIS public permissionless DEX description as a model, not a product-specific guarantee.
  5. Inventory dependencies. Check whether the workflow relies on an interface, relayer, administrator, or off-chain order component. Distinguish what documentation confirms from what remains unknown.
  6. Assess concentration in context. If decentralization is relevant to an operational decision, assess the specific network, asset, and application over a defined time window. A stated ethos is not a substitute for evidence about de facto concentration.
  7. Review liquidity claims carefully. If payment or settlement capacity is part of the review, identify the relevant obligations, currencies, and conditions being assessed. Treat the PFMI liquidity principle as an operational analogy unless the infrastructure is a designated FMI; it does not automatically apply to every crypto product.
  8. Keep conclusions within the evidence. State which behavior is documented, which is implementation-dependent, and which question has not been verified. Avoid turning an architectural description into an assurance about security, availability, recovery, or outcomes.

In simple terms, DeFi is best understood by tracing the user-facing interface, application logic, settlement system, and dependencies as separate parts of one workflow. The category label can orient a review, but the implementation and its evidence determine what a specific system does and where its control boundaries lie.

Sources and references