Hash objects are similar to Arrays in that they are a collection. However, Hashes are more similar to dictionaries in that they have keys, or terms, that relate to their values, or definitions. Any object can be used as a key, including other hashes. Hashes are known as associative arrays and use bracket notation to retrieve elements. Unlike Arrays, Hashes use the keys to retrieve the values.
Example: hash = { a: 1, b: 2, c: 3 } hash #=> 1