Uniswap is a decentralized exchange that facilitates automated transactions between Ethereum-based tokens. It is designed to be an open-source platform with an automated market maker (AMM) model. Instead of using an order book, token trades are facilitated directly between users through a liquidity pool and prices orders with an algorithm that relies on the equation x*y=k to create a price spectrum for token pairs available in the liquidity pools provided by other users. Uniswap tokens are used as a governance token and as an incentive for users to fund the liquidity pools. Since the platform is decentralized, all the trading fees collected are distributed among the liquidity providers; according to the share that they provide in the liquidity pools.
Uniswap is one of the largest decentralized exchanges (DEX) and one the largest cryptocurrency exchanges overall by daily trading volume. The platform was originally created by Hayden Adams, a former mechanical engineer at Siemens. It is backed by some influential venture capital funds, including: Andreessen Horowitz, Paradigm Venture Capital, and Union Square Ventures.

Newdex is the first EOS based decentralized exchange. It's built on the EOS main chain and uses an off-chain matching mechanism to pair buyers and sellers. Newdex was hacked in September 2018, and lost around $58,000 worth of cryptocurrencies. Trading fees are 0.1%.

PancakeSwap is a decentralized exchange built on the Binance blockchain. It allows users to stake their funds in return for the protocol’s tokens, and uses an automated market maker (AMM) model to enable users to trade BEP-20 tokens on the platform without an order book. PancakeSwap is similar to Uniswap and SushiSwap, and rewards users for depositing funds to the liquidity pool with PancakeSwap tokens that entitle holders to a portion of the trading fees generated on the platform.