DeFi coins are cryptocurrency tokens used in the DeFi (Decentralized Finance) ecosystem, which applies blockchain technology and smart contracts to create decentralized financial applications and services. Unlike traditional financial systems, DeFi does not depend on centralized institutions and regulators. Instead, it is based on the principles of decentralization, where management and control are distributed among network participants.

Decentralized Finance (DeFi) has become a popular term in the cryptocurrency world, and many DeFi coins (tokens) have emerged in recent years. Some popular DeFi coins (tokens) include:

1. Ethereum (ETH) - Ethereum is the second-largest cryptocurrency by market capitalization and the foundation for most DeFi projects. It's a decentralized, open-source blockchain that allows developers to create smart contracts, which are self-executing contracts that automatically enforce the terms of an agreement.

2. Uniswap (UNI) - Uniswap is a decentralized exchange (DEX) that allows users to trade cryptocurrencies without intermediaries. It uses an automated market maker (AMM) algorithm to determine the price of tokens, and users can earn fees by providing liquidity to the platform.

3. Aave (AAVE) - Aave is a decentralized lending platform that allows users to borrow and lend cryptocurrencies without intermediaries. It uses a pool-based system to match borrowers with lenders, and users can earn interest by providing liquidity to the platform.

4. Compound (COMP) - Compound is a decentralized lending and borrowing platform that allows users to earn interest on their cryptocurrency holdings and borrow funds by using their cryptocurrency as collateral. It uses an algorithm to determine interest rates based on supply and demand.

5. Chainlink (LINK) - Chainlink is a decentralized oracle network that provides secure, tamper-proof data feeds to smart contracts on the blockchain. It connects smart contracts to real-world data and events, enabling them to execute automatically.

6. MakerDAO (MKR) - MakerDAO is a decentralized lending platform that allows users to borrow a stablecoin called DAI, which is pegged to the value of the US dollar. It uses a system of collateralized debt positions (CDPs) to ensure the stability of the DAI stablecoin.

7. Synthetix (SNX) - Synthetix is a decentralized platform that allows users to trade synthetic assets that track the value of real-world assets, such as stocks, commodities, and currencies. It uses a system of collateralized debt positions (CDPs) to ensure the stability of the synthetic assets.

These are just a few examples of popular DeFi coins (tokens), and there are many more emerging in this fast-paced industry.