PostgreSQL is an Object-Relational Database Management System (ORDBMS) that has been developed in various forms since 1977. It began as a project named Ingres at the University of California at Berkeley. Ingres itself was later developed commercially by Relational Technologies/Ingres Corporation.
In 1986 another team led by Michael Stonebraker from Berkeley continued the development of the Ingres code to create an object-relational database system called Postgres. In 1996, due to a new open source effort and the enhanced functionality of the software, Postgres was renamed to PostgreSQL, after a brief stint as Postgres95. The PostgreSQL project is still under very active development worldwide from a team of open source developers and contributors.
PostgreSQL is widely considered to be the most advanced open source database system in the world. It provides many features (which are discussed in more detail in the section titled PostgreSQL Feature Set) that are traditionally seen only in enterprise-caliber commercial products.