In short Decentralized Autonomous Organization — a community that coordinates through on-chain voting, with rules and treasury enforced by smart contracts.
Voting power usually tracks tokens held, which means a DAO is closer to a shareholder meeting than to one-person-one-vote — and concentrated holdings quietly decide most outcomes. The genuinely new part is enforcement: an approved proposal can move the treasury automatically, without a director signing anything. In practice most DAOs delegate day-to-day work to small elected groups, because voting on everything is slower than it sounds.