Query optimization is the process of improving the efficiency of a database query to ensure it runs faster and uses fewer resources. This involves analyzing the query structure, the underlying data, and the database's execution plan to identify potential improvements. By optimizing queries, databases can return results more quickly, which enhances overall performance. Techniques include rewriting queries for better logic, using appropriate indexes, and minimizing data retrieval. Effective query optimization is essential for maintaining the responsiveness of applications that rely on large datasets.