Query performance refers to how efficiently a database processes a request for data. It is measured by factors such as response time, resource usage, and the speed at which results are returned. Optimizing query performance is essential for ensuring that applications run smoothly and users receive information quickly. Several techniques can enhance query performance, including indexing, which allows the database to find data faster, and query optimization, which restructures queries for better execution. Tools and metrics, such as SQL execution plans, help database administrators identify bottlenecks and improve overall performance.