The experimental blockchain platform and Polkadot's cousin
Kusama was built by Parit Technologies, the same team who created Polkadot. Kusama is an interoperable and scalable blockchain network that was built on Substrate and has almost similar codebase as Polkadot. Hence, it is known as Polkadot's cousin. It uses Nominated Proof-of-Stake (NPoS) consensus mechanism. The network is considered as an experimental network that focuses on providing a real environment for developers to experiment and develop.
KSM is the native token for Kusama network which is use to validate network, nominate validators, bond parachains and act as governance token, giving rights to holders to have a say in future development of the network.