Arrays and hashes are both structured like lists and every slot in the list acts like a variable. Each slot points to a particular object. Arrays are indexed with numbers that start with 0 and go up to the array’s length minus one. Hashes are collections of key-value pairs. You would use a hash if you don’t want to use numbers as indices or if you want to use unordered numeric indices. With a hash, you can use any Ruby object for a key or value.
To create an array use the following syntax:
array = [value1, value2, value3]
To create a hash use the following syntax:
hash = { :key1 => value1, :key2 => value2, :key3 => value3 }