What is the conceptual difference between an array and a hash?

Array - is an ordered collection of elements, accessed by their numeric index.

Hash - is an unordered collection of key-value pairs, accessed by their keys.

Main differences:

Attribute	Array	Hash
Order	Preserves insertion order	Does not preserve insertion order
Access	By integer index	By key of any type
Keys	Indices are always integers	Keys can be of various types

Example:

# Array
arr = [10, 20, 30]
puts arr[0] # => 10

# Hash
hsh = { a: 10, b: 20, c: 30 }
puts hsh[:a] # => 10