1. There are three main types of decentralized exchanges (DEXes): orderbook-based DEXes where makers create limit orders and takers fill them, liquidity-based DEXes that use liquidity pools, and aggregators that search across DEXes to find the best price. 2. Orderbook DEXes include EtherDelta, 0x, and AirSwap, while popular liquidity DEXes are Uniswap, Bancor, and Balancer. Kyber and 1inch are examples of aggregators that combine liquidity from various sources. 3. DEX aggregators aim to solve the problem of liquidity fragmentation by allowing traders to get the best price through a