Database extensions are additional features or functionalities that enhance the capabilities of a database management system (DBMS). They can provide new data types, functions, or tools that allow users to perform more complex queries and operations. For example, a PostgreSQL extension might enable advanced geospatial queries, making it easier to work with location-based data. These extensions can be developed by the database community or third-party vendors and are often designed to integrate seamlessly with existing database systems. Users can install and configure these extensions to tailor their databases to specific needs, improving performance and usability for various applications.