--- title: "What Is DeFi? A Plain-English Guide to Decentralized Finance" description: "Decentralized finance — DeFi — lets people lend, borrow, trade and earn yield through software running on public blockchains, cutting out banks and brokers. It holds roughly $70 billion in deposits. Here's how it works, why people use it, and where the real dangers lie." category: "Crypto" category_url: https://boursel.com/category/crypto author: "Kenji Nakamura" published: 2026-06-26T03:48:00.000Z updated: 2026-06-26T03:48:00.000Z canonical: https://boursel.com/article/what-is-defi-a-plain-english-guide-to-decentralized-finance tags: ["defi", "ethereum", "smart-contracts", "crypto", "explainer"] --- # What Is DeFi? A Plain-English Guide to Decentralized Finance Decentralized finance — DeFi — lets people lend, borrow, trade and earn yield through software running on public blockchains, cutting out banks and brokers. It holds roughly $70 billion in deposits. Here's how it works, why people use it, and where the real dangers lie. *This is general information, not investment advice. DeFi carries serious risks, detailed below.* In traditional finance a bank holds your money and decides who gets a loan. DeFi tries to replace that middleman with code anyone can read. ## The core idea Decentralized finance, or DeFi, is a catch-all for financial services — lending, borrowing, trading, earning yield — delivered by software on public blockchains instead of by banks or brokerages. Most of it runs on **Ethereum**, with meaningful activity on chains like Solana too. The defining feature is the absence of a central middleman: you keep funds in your own crypto **wallet** and interact directly with the software — no application, no credit check, no business hours. ## Smart contracts: the engine Every DeFi service runs on **smart contracts** — self-executing programs stored on a blockchain that run automatically when their conditions are met. As [Ethereum's own documentation](https://ethereum.org/en/defi/) puts it, once deployed they "always run as programmed"; no company can quietly change them. Because the code is public, anyone can inspect exactly what a protocol does — DeFi's great strength, and its great weakness, since attackers can read the same code for flaws. ## The building blocks - **Decentralized exchanges (DEXs)** like Uniswap let users swap tokens with no central order book. Most use an **automated market maker**: instead of matching buyers and sellers, they draw on **liquidity pools** — reserves of token pairs funded by users who deposit assets and earn a cut of trading fees. - **Lending protocols** like Aave and Compound run loan markets with no credit check. They require **over-collateralization** — you lock up *more* crypto than you borrow (often 125–200%); if your collateral falls too far, it's automatically sold to repay the loan. - **Stablecoins** — tokens pegged to the dollar — are the unit of account that makes lending and yield workable without constant currency risk. - **Yield farming and staking** let users earn interest, fees or tokens for supplying capital or helping secure a network. The standard size gauge is **total value locked (TVL)** — the dollar value of all assets deposited in DeFi. Per [DefiLlama](https://defillama.com/), TVL sits around **$70 billion**, down from over $110 billion at the start of 2026 and well below the late-2021 peak near $177 billion, with Ethereum holding about half. Treat any figure as a snapshot — it swings with prices and flows. ## Why people use it Three structural draws: **permissionless access** (anyone with a wallet and internet can use it, no minimum or gatekeeper); **transparency** (every transaction and reserve is on a public ledger, unlike an opaque bank balance sheet); and **composability** — protocols snap together like "money legos," so a user can lend, borrow and reinvest across services in a single transaction. ## The risks are real DeFi's openness cuts both ways, and the dangers are not hypothetical. - **Smart-contract exploits.** A bug can be catastrophic. Cumulative DeFi-related hack losses run into the **billions of dollars**, including bridge attacks like Ronin ($625 million, 2022) and Wormhole ($320 million, 2022). Big exploits have continued since. - **Volatility and liquidation.** Because loans are backed by volatile crypto, a sharp drop can trigger cascading automatic liquidations that wipe out borrowers fast. - **Scams and "rug pulls."** Anyone can launch a protocol; fraudulent ones lure deposits and vanish. There's no deposit insurance, no FDIC, and usually no legal recourse. - **Regulatory uncertainty.** Rules are still forming. The 2025 U.S. **GENIUS Act** set a framework for the stablecoins DeFi runs on, and other measures are moving through Congress, but much remains unsettled. ## A short history DeFi cohered in "**DeFi Summer**" 2020, when Compound began paying users tokens to deposit assets, sparking a rush of capital. TVL leapt from under $1 billion to tens of billions within months and peaked near $177 billion in late 2021 before collapsing with the broader crypto bust of 2022 — including the implosion of the algorithmic stablecoin TerraUSD. It has not returned to those highs. ## Where it stands DeFi remains a significant, volatile and contested corner of finance. Its architecture — open code, no intermediaries, self-custody — is a genuine departure from the traditional system. Whether that proves durable depends on whether it can curb exploit losses, absorb regulation, and reach users beyond the crypto-native — open questions, not settled ones. For anyone exploring it, the cardinal rule is that self-custody means self-responsibility: there is no bank to call when something goes wrong. ## Sources - [What is DeFi?](https://ethereum.org/en/defi/) - [DefiLlama — DeFi dashboard](https://defillama.com/)