0x is a decentralized exchange built on the Ethereum blockchain that allows for ERC20 tokens to be traded. 0x’s intention is to serve as a building block from which others can easily create their own decentralized exchange.
One of the key differences between 0x and other decentralized exchanges is that 0x is fast. To reduce blockchain bloat, all orders are transported off-blockchain and later verified. In addition to making transactions quick, this removes the necessity of spending gas to pay for network transaction costs, like on other decentralized exchanges such as EtherDelta.
0x uses a open-source system of smart contracts which acts as an infrastructure for those wishing to build with the 0x protocol. A number of projects have already started building on the 0x platform already such as Augur, Aragon and Request Network.