Psql is a command line program that acts as the primary front-end to a Postgresql database. It provides a number of shell commands (pg_dump to dump the content of a database, createdb to create a database, and many others). It also has a number of meta commands to list elements and display information (see the Psql cheatsheet information box).
d __table__: Show table definition, including triggers
dt : List tables
df: List functions
dv: List views
x: Pretty-format query results instead of the not-so-useful ASCII tables
connect __database__: Connect to a database
l: List databases
Adding a + on a d command will show more results: compare, for instance, d titanic with d+ titanic ...