The postgresql contrib package provides several additional features for the postgresql database. this version is built to work with the server package postgresql-9.3. contrib often serves as a testbed for features before they are adopted into postgresql proper:

adminpack - file and log manipulation routines, used by pgadmin
btree_gist - b-tree indexing using gist (generalised search tree)
chkpass - an auto-encrypted password datatype
cube - multidimensional-cube datatype (gist indexing example)
dblink - functions to return results from a remote database
earthdistance - operator for computing the distance (in miles) between
two points on the earth's surface
fuzzystrmatch - levenshtein, metaphone, and soundex fuzzy string matching
hstore - store (key, value) pairs
intagg - integer aggregator/enumerator
_int - index support for arrays of int4, using gist (benchmark
needs the libdbd-pg-perl package)
isn - type extensions for isbn, issn, ismn, ean13 product numbers
lo - large object maintenance
ltree - tree-like data structures
oid2name - maps oids to table names
pageinspect - inspection of database pages
passwordcheck - simple password strength checker
pg_buffercache - real time queries on the shared buffer cache
pg_freespacemap- displays the contents of the free space map (fsm)
pg_trgm - determine the similarity of text based on trigram matching
pg_standby - create a warm stand-by server
pgbench - tpc-b like benchmark
pgcrypto - cryptographic functions
pgrowlocks - a function to return row locking information
pgstattuple - returns the percentage of dead tuples in a table; this
indicates whether a vacuum is required.
postgresql_fwd - foreign data wrapper for postgresql
seg - confidence-interval datatype (gist indexing example)
spi - postgresql server programming interface; 4 examples of
its use:
autoinc - a function for implementing autoincrement/
identity
insert_username - function for inserting user names
moddatetime - update modification timestamps
refint - functions for implementing referential
integrity (foreign keys). note that this is
now superseded by built-in referential
integrity.
timetravel - re-implements in user code the time travel
feature that was removed in 6.3.
tablefunc - examples of functions returning tables
uuid-ossp - uuid generation functions
vacuumlo - remove orphaned large objects
postgresql is an object-relational sql database management system.