PostgreSQL is an open-source relational database that is currently the most popular of its kind. It offers many relevant extensions to the relational model, such as PostGIS geospatial support, ACID compliance, easy implementation of custom datatypes, custom functions, and the use of different programming languages without recompiling the engine. PostgreSQL is a very powerful database engine for a vast number of use cases. Extremely efficient and secure, with huge adoption, PostgreSQL is a solid choice when it comes to open-source databases for now and the foreseeable future.