DOT is the native token for the Polkadot multi-chain network, or 'blockchain of blockchains'. Polkadot is famously founded by Gavin wood (a co-founder of Ethereum) in 2016 and it aims to create an interconnected internet for blockchain networks.
DOT can be used to stake for transaction validation on Polkadot, the governance of Polkadot and bond external chains (Parachains) to the network.