JOIN is a method of combining (joining) information from two tables. The result is a stitched set of columns from both tables, defined by the join type (INNER/OUTER/CROSS and LEFT/RIGHT/FULL, explained below) and join criteria (how rows from both tables relate).
A table may be joined to itself or to any other table. If information from more than two tables needs to be accessed, multiple joins can be specified in a FROM clause.
[ { INNER | { { LEFT | RIGHT | FULL } [ OUTER ] } } ] JOIN
Joins, as their name suggests, are a way of querying data from several tables in a joint fashion, with the rows displaying columns taken from more than one table.