Cosmos, also known as the Internet of Blockchains, is an ecosystem built for interoperability among different blockchain networks. Its technology allows a network of multiple blockchains to communicate with each other through its IBC (Inter-Blockchain Communication) protocol to exchange data and assets conveniently.
Cosmos is a Proof of Stake Layer-3 blockchain, which makes it possible for decentralized applications to achieve more scalability through interoperability. ATOM is the native token within the Cosmos ecosystem which serves three purposes - for preventing spam, for staking, and as a governance token for voting on proposals to develop the Cosmos Hub.