0x is a liquidity protocol that enables the peer-to-peer exchange of assets on the Ethereum blockchain. The protocol establishes a standard set of rules that traders, applications, and market makers can abide by in order to safely & trustlessly trade with each other.
0x labs operates 0x API, a decentralized exchange liquidity aggregator that taps into Uniswap, Curve, and others in addition to native 0x protocol orders. 0x API powers matcha.xyz, a simple swap application maintained by the 0x Labs team.