Introduction to Two Pointers Pattern

In problems where we deal with sorted arrays (or linked-lists) and need to find a set of elements that fulfill certain constraints, the Two Pointers approach becomes quite useful. The set of elements could be a pair, a triplet or even a subarray. For example, take a look at the following problem:

Given an array of sorted numbers and a target sum, find a pair in the array whose sum is equal to the given target.