An array is a collection of memory locations that store elements of the same data type. Arrays have a fixed size and elements are accessed using an index. This document discusses array implementation using Python's array module. It describes how to create an array, access elements, insert/delete elements, search, update values, and traverse through an array. The key differences between arrays and lists in Python are that arrays have a fixed size and can only contain same-type elements, while lists can grow/shrink and hold mixed types.