A DeFi aggregator is a platform that consolidates various decentralized finance protocols and services into a single interface, optimizing the user experience. It helps users find the best rates, such as the highest staking, borrowing, or liquidity provision yield. By integrating multiple protocols, DeFi aggregators streamline decentralized finance by reducing the time and complexity of managing assets across different platforms. Examples include Yearn Finance and 1inch, which aggregate liquidity and optimize DeFi strategy execution.