A hash is a set of key-value pairs. The keys are strings that are unique in the given hash. The values are scalars, including references to other data structures. In PHP they are calle "associative arrays". In Python "dictionaries".
( 'name' => 'Foo Bar', 'email' => 'firstname.lastname@example.org', )
( 'banana' => 7, 'apple' => 3, 'lemon' => 1, )