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Encyclopedia DeFi · Entry 46

What is DeFi? Financial applications built from smart contracts

AI-assisted research · separate automated verificationCorrections

Theme
DeFi
Sources
3 cited records
Reading time
About 3 minutes
Automated verification
Substantive update
In this article

At a glance

Key facts

Key facts for What is DeFi? Financial applications built from smart contracts
FactDetailSource
ExecutionContract rules determine allowed state changes.[1]
ExampleAave V3 separates supplying assets, borrowing and repayment.[2]
ControlRoles can authorize privileged actions in a contract.[3]
01

Separate the application into its parts

A DeFi screen combines several different things: a blockchain that records execution, tokens that represent assets, contracts that hold balances and apply rules, and an interface that prepares requests. The website can disappear while the contracts remain on the chain. A contract can also depend on services that the website does not make obvious.

Decentralization is therefore a question about particular powers. Who can change the implementation, pause withdrawals, replace an oracle or issue the asset? An answer about validators does not answer those questions about an application.

02

Follow a simple lending example

Imagine a lending market where Alice supplies 1,000 units of a token. Bob supplies a different accepted asset as collateral and borrows 100 units from that market. The contracts record a supply claim for Alice and debt for Bob. Their positions do not become a private agreement between the two people.

Bob must satisfy the market’s collateral rules. Alice’s ability to withdraw depends on available liquidity and the rules of her position. This example describes pooled lending; an exchange pool instead changes token inventory when someone trades.

03

What a successful transaction establishes

Successful execution establishes that the chain accepted the requested operation under the contract’s rules. It does not establish that the token has sound backing, that a quote was favorable or that a contract contains no exploitable error. Those are separate questions.

Start an investigation with the exact chain, contract and version. Then identify the asset, accounting, withdrawal path, external prices and administrative roles. The linked entries explain these components separately so that a familiar brand name does not substitute for understanding the mechanism.

Direct answers

Questions people ask

Does DeFi always mean nobody can change the rules?

No. A contract can assign privileged roles, and an application may use an upgradeable implementation. Inspect the actual administrative powers rather than infer immutability from the DeFi label.

Inspect the evidence

The answer and key facts have stable claim links. These records retain the scope and qualification when reused.

DeFi is a group of financial applications that use blockchain contracts to carry out activities such as exchanging tokens and managing collateralized loans. An application can have public settlement while still depending on administrators, data feeds, token issuers and a particular website.

Scope: DeFi. Verification: verified · 2026-10-02T15:08:18.373Z.

Link to this claim
Execution: Contract rules determine allowed state changes.

Scope: DeFi. Verification: verified · 2026-10-02T15:08:18.373Z.

Link to this claim
Example: Aave V3 separates supplying assets, borrowing and repayment.

Scope: DeFi. Verification: verified · 2026-10-02T15:08:18.373Z.

Link to this claim
Control: Roles can authorize privileged actions in a contract.

Scope: DeFi. Verification: verified · 2026-10-02T15:08:18.373Z.

Link to this claim
Revision history
  1. — First publication after primary-source research and independent automated verification.
  2. — Before first publication, independent review checked and revised: prerequisites. Read Ethereum’s definition and contract mechanisms, Aave supply/borrow/withdraw, and OpenZeppelin ownership/roles. QA and facts correctly distinguish public contract execution from administrative decentralization. The Alice/Bob lending illustration states pooled accounting and conditional withdrawal. Changed prerequisite to Ethereum smart contracts so the reading path introduces the actual mechanism.

On the Understand a swap path · Learn next: Decentralized exchanges: how a token trade reaches settlement

Source register

Sources and references

Retrieval dates and locators are recorded individually.
  1. Ethereum DeFi overviewethereum.org contributors

    Financial applications and the distinction between blockchain, assets, protocols and interfaces.

    Locator: What is DeFi?; How does DeFi work? · Retrieved: 2026-10-02Open source
  2. Aave V3 PoolAave

    Pool operations, collateral restrictions and liquidation settlement.

    Locator: supply; withdraw; borrow; repay; liquidationCall · Version / scope: Aave V3 · Retrieved: 2026-10-02Open source
  3. Access controlOpenZeppelin

    Ownership, roles, administrator authority and timelock limitations.

    Locator: Ownership and Ownable; Role-Based Access Control; Delayed operation · Version / scope: OpenZeppelin Contracts 5.x · Retrieved: 2026-10-02Open source
How this article was made

Research and drafting use AI assistance. A separate automated review checks claims against primary sources; no external expert or named human review is implied. Publication, substantive editing, source retrieval and verification are recorded separately. This version was independently checked by an automated reviewer on 2 October 2026.

Editorial method and corrections

Degrees of Satoshi editorial project. “What is DeFi? Financial applications built from smart contracts.” Published 2026-10-02; updated 2026-10-02. https://degreesofsatoshi.com/encyclopedia/what-is-defi/