0x (Zero-ex) is the name of a cryptocurrency platform. The platform has a native token called ZRX. The platform is an “open protocol for decentralized exchange on the Ethereum blockchain.” The token allows one to have a say in protocol upgrades.
In simple terms, 0x (Zero-ex) is an open source platform for facilitating peer-to-peer exchange and building out decentralized exchanges that allow users to trade Ethereum-based tokens (from ZRX, to ETH, to any token built on that network).
0x has been in the works since 2016 (it has some longevity at this point), it is built on top of the Ethereum platform, and has a native cryptocurrency token also called 0x that trades under the ticker ZRX.
In terms of price history, ZRX had a rather democratic launch and has historically preformed well compared to other tokens.
That is the very short version, you can get the much more exciting version of everything 0x can do and everything ZRX can be used for on 0x.org.
So, why is the above “good?”
It is “good” because 0x solves some existing problems related to decentralized exchanges in terms of interoperability and fees via an open source project.
Currently decentralized exchanges (crypto exchanges not run by any central entity) tend to rely directly on a blockchain (so everything done on the exchange incurs transaction fees and needs to be added to the chain by miners; most decentralized exchanges are built on Ethereum’s blockchain, so there is a problem there specifically). Further, the current decentralized exchanges, for example EtherDelta and Oasis, can’t interact with each other and aren’t built using a standard protocol.
0x offers a single protocol standard and an off-chain order book solution that mostly solves those problems.
So, the whole idea of a decentralized exchange is to ensure trades happen on the blockchain, where funds are more secure.
To explain further, 0x works something like this: A “maker” broadcasts his or her order. A “relayer” then posts that order in an off-chain order book and a counterparty (called a “taker”) accepts the order by pushing the transaction into the project’s DEX smart contract.
– From Forbe’s analysis of 0x
All that said, I think the best description of what 0x is and why it is good can be found on the official site and 0xproject blog. Also, for a more in-depth look at how 0x allows for peer-to-peer exchanges, check out that A beginner’s guide to 0x or the Forbes article above.