DataLoader is a utility for batching and caching data fetching in Node.js and JavaScript applications. It's particularly useful in GraphQL implementations to prevent the "N+1" problem, where multiple database calls are made when resolving related data. DataLoader optimizes data retrieval by aggregating individual requests into a single, efficient batched request, and remembers the results to avoid redundant calls. This significantly improves performance and reduces database load, ensuring smoother and faster data access.