A brief history
Will Warren and Amir Bandeali co-founded 0x in October 2016. Their initial intention was to provide a standard method of trading any Ethereum token on the blockchain. Unlike many other Ethereum decentralized exchange protocols, 0x supports both fungible (ERC20) and non-fungible (ERC-723) tokens. This means it can be used for the permissionless trading of a wide range of assets. What makes the 0x protocol unique compared to other DEX protocols is its hybrid off-chain relay, and on-chain settlement architecture. Having trade settlements occur on-chain and storing orders off-chain makes 0x a flexible and gas-efficient DEX protocol. Users who create 0x orders are called “makers” and users who fill those orders are called “takers.” When creating an order, makers will indicate the details of that order- the tokens they wish to exchange and the price at which they are willing to exchange them. If the maker does not already know their desired counterparty to send the order to directly, there are ​"relayers" that help traders create, find, and fill 0x orders.

ZRX in practice
ZRX is the protocol's governance and liquidity token it's an essential aspect of 0x’s decentralization. Liquidity providers/market-makers stake ZRX tokens to receive a liquidity reward funded through a protocol fee applied to every 0x trade. The fee is denominated in ETH and deposited into a staking contract, and fees are pooled within the staking contract over a fixed window of time, which is referred to as an epoch. At the end of each epoch, liquidity providers collect a portion of the accumulated pool. These providers can also establish a 0x staking pool that allows ZRX token holders to delegate stakes to them. Most Proof-of-Stake systems use a fixed return percentage, however, 0x differs in that its staking returns are dynamic. This means that as more volume flows into the 0x network, the protocol fees and staking rewards grow proportionally. Additionally, ZRX holders can vote on 0x Improvement Proposals which can change the behaviour of the 0x pipeline of smart contracts. This could also extend to off-chain tooling proposals if it relates to how the contracts are interacted with.