Another strength of PostgreSQL is its extensibility. Extensibility was one of the original design goals, going back to the late 1980s. Now, in PostgreSQL 9.4, there are many additional modules that plug into the core PostgreSQL server.
There are many kinds of additional module offerings, such as the following:
Note that many tools and client interfaces work with PostgreSQL without any special installation. Here, we are discussing modules that extend and alter the behavior of the server beyond its normal range of SQL Standard syntax, functions, and behavior.
The procedure that makes a module usable is actually a two-step process. ...