PostgreSQL is an open source relational database, which works on client/server technology. PostgreSQL offers a unique range of features that compare to the major commercial databases such as DB2, Sybase, Oracle etc.
Being open source proves to be a biggest advantage of the postgreSQL i.e you can see the source code for PostgreSQL. It is not owned by any single company. It is developed, maintained, broken, and fixed by a group of volunteer developers around the world. This relational database is totally free, you don’t have buy it, niether will You have to pay any maintenance fees.
PostgreSQL includes all the features of a relational database and it also encorporates some of its unique features. PostgreSQL offers inheritance, user can add own data types to PostgreSQL. Most database systems allow you to give a new name to an existing type. Some systems allow you to define composite types.Other than all this here you can add new fundamental data types. It also includes support for geometric data types such as point, polygon, circle, line segment and box. It uses the Indexing structure which makes this geometric data types very fast.
As explained above it is built in client-server architecture, it can build number of clinet applications in different languages as C,C++,Python,PL and JAVA and many others. On the server side it supports a powerful procedural language, PL/pgSQL .
You can add procedural languages to the server.Procedural languages support Perl, TCL/Tk, and bash shell.