A decentralized cryptocurrencyexchange that was a fork of Uniswap. This was originally built on the Ethereum network to enable traders to swap ERC-20 tokens. As the EVM was forked, Sushiswap expanded to handle the tokens created on the ensuing blockchains.
Smart contracts are utilized to create liquidity pools that allow for individuals to swap tokens without going through any custodian or intermediaries. Token holders have the option of becoming liquidity providers themselves with many platforms offering returns as incentive for participating.
This is all part of decentralized finance (DeFi) where exchanges of this sort are providing a viable alternative to their centralized counterparts. These operate without an order book, instead opting for the automated market maker (AMM) approach.
Sushiswap has its own token: $SUSHI.