Uniswap is a decentralized cryptocurrency exchange protocol built on the Ethereum blockchain. It allows for the swapping of ERC-20 tokens, which are the most common type of tokens on the Ethereum network, without the need for intermediaries like centralized exchanges or order books.

Uniswap uses an automated market-making (AMM) mechanism to determine prices and execute trades. This means that trades are executed against a liquidity pool instead of against an order book, and prices are determined by a mathematical algorithm based on the ratio of tokens in the pool.

Users can contribute tokens to the liquidity pool and earn fees in proportion to their contribution. The Uniswap protocol has its own native token called UNI, which can be used for governance and decision-making in the platform.

Uniswap has become one of the most popular decentralized exchanges in the cryptocurrency space, with a large community of users and developers contributing to its growth and development.