A hash is also used to refer to an associative array. I.e. an array indexed by
something other than an integer. The index is usually referred to as a key. Internally, this association is done via a hash table. In some programming languages you can only use strings as the key, in others you can use full-blown objects. They are very powerful constructs, and greatly simplify many coding tasks. Perl and Python are two languages that make good use of hashes by including them as built-in types (although they're known as dictionaries in python).