The Hash is a collection for storing items. Items area stored against a key value, which can be used to retrieve them. It differs from the Array class, as it allows you to use any object for this key, rather then just whole numbers.
// create a new hash myHash = { key : value, key2 : value }
// set value to a hash myHash[ key ] = new Value()
// get value from a hash myVal = myHash[ other_key ]
You can set and get values from the Hash using standard array notation.