Quick Ref.
Functions
date
number
string
Data Types
date
number
string
Name of the server postgres
Name of the client psql
Typical command line to start the client psql -h server -d dbname -U username
server
the internet address of a computer running the server
dbname
the name of the database to use
username
database user name
Useful commands
\?
\dt
\i file.sql
\c otherdbname
Beware!

If results are wide the format is unreadable. \pset pager

Thanks to Nicola Boni from Italy for supplying this.