The Görli testnet initiative is a development campaign to create the first cross-client proof-of-authority network for Ethereum. There are various testnets available for experimenting with contracts and d-apps before going live on the public chain. However, there is no testnet available that is both widely usable across all clients, and robust enough to guarantee consistent availability and high reliability. This is what Görli tries to be.
There are many Ethereum testnets available for experimenting with smart contracts and deploying decentralised applications before going live on the main Ethereum network. However, there is no testnet available that is both widely usable across all client implementations, and robust enough to guarantee consistent availability and high reliability.