PostgreSQL is a open source object-relational database management system. PostgreSQL is free and itís an alternative to other open-source database systems like MySQL.
PostgreSQL is a highly scalable, SQL compliant object-relational database management system. PostgreSQL has more than 15 years of development history.
PostgreSQL is based on POSTGRES, Version 4.2, which was developed at the University of California at Berkeley Computer Science Department. POSTGRES introduced many new database concepts that became available in other commercial database systems later.
PostgreSQL supports SQL92 and SQL99 and has many important database features like - triggers, views, complex queries, foreign keys, transactional integrity, aggregate functions, etc.
PostgreSQL is an open source project and as such can be used, modified, and distributed by everyone free of charge for any purpose, even commercial.