As 0x project’s whitepaper described “0x is an open protocol for decentralized exchange on the Ethereum blockchain.” In simple terms, 0x defines all the rules which an exchange need’s to perform trade functionality. Anyone can build a decentralized exchange using 0x protocol. Linda Xie wrote an awesome blog about 0x protocol which you can read here.
This is a companion discussion topic for the original entry at https://blog.crowdbotics.com/a-beginners-guide-to-building-a-relayer-with-0x-protocol/