Hi, roysolomon.
I found this here:
http://en.wikipedia.org/wiki/Hash_table
"In computer science, a hash table, or a hash map, is a data structure that associates keys with values. The primary operation it supports efficiently is a lookup: given a key (e.g. a person's name), find the corresponding value (e.g. that person's telephone number). It works by transforming the key using a hash function into a hash, a number that the hash table uses to locate the desired value."
Example (a small phone book as a hash table):
