Kovan is a testnet that was created by the guys at Parity, who wanted a new type of PoA network where developers could deploy their smart contracts, knowing that they will stay running endlessly given that this network is highly secure. This network is the fastest of them all because it has a 4-second block time, which makes testing a breeze, since you don't have to wait for long confirmation times.
It was born because of the attack conducted on Ropsten in 2017 when Parity realized that developers were losing an important tool in their arsenal, given that they need to test their smart contracts on the most realistic scenarios possible to emulate blockchain limitations.
Kovan is one of the most active networks, since they provide Kovan Improvement Proposals, known as KIPs, where users can submit GitHub issues on the repository (https...