Instead of directly executing trades on-chain, users only sign their swap intention and delegate the execution to so-called solvers (aka relayers in other protocols). Solvers bid on the best possible exchange rate in order to win the right to settle trades. By batching multiple trades together in order to create CoWs (Coincidence of Wants), solvers can save on gas costs, AMM fees and execution risk. Therefore CoWs lead to structurally better prices than on any existing DEX aggregator. In the absence of CoWs solvers fall back to using the best possible on-chain route, by comparing quotes from leading aggregators.
COW token allows its holders the right to govern and curate the infrastructure of the CoW Protocol ecosystem through the CowDAO. Additionally, COW token holders receive fee discounts when trading on CowSwap & some other perks.