Kusama is designed to provide a massively interoperable and scalable framework for developers. It has the same code base as Polkadot. It was created by the same team of Polkadot and the same company known as Parity Technologies. It was founded by Dr. Gavin Wood, the co-founder of Ethereum.
The network has an extensive team of successful blockchain engineers and has over 100 employees. The Web3 Foundation supports Kusama with research and community development.
In simple words, it is a platform where developers can test and experiment with new blockchains or applications that are meant for the Polkadot network. Developers can test their products on Kusama with real cryptocurrency traded on the open market. Official Polkadot upgrades are also tested on Kusama before their release.