Polkadot is an open-source sharded multichain protocol that connects and secures a network of specialized blockchains, facilitating cross-chain transfer of any data or asset types, not just tokens, thereby allowing blockchains to be interoperable with each other.
Self-described as "Polkadot's wild cousin," Kusama is an experimental blockchain platform that is designed to provide a massively interoperable and scalable framework for developers.
Solana is a highly functional open source project that banks on blockchain technology’s permissionless nature to provide decentralized finance (DeFi) solutions. While the idea and initial work on the project began in 2017, Solana was officially launched in March 2020 by the Solana Foundation with headquarters in Geneva, Switzerland.