The Stack Collection

The System.Collections.Stack collection mimics the same-named memory area and works according to the LIFO (Last-In, First-Out) paradigm meaning that the last item you add to the collection is the first that is pulled out from the collection. Stack exposes three important methods: Push that adds an item to the collection, Pop that allows consuming and removing an item from the collection, and Peek that returns the top item in the collection without removing it. The following is an example:

As for Queue, here you work with Object items. Although this enables pushing different kinds of objects to the collection, it is not a good idea. You should prefer the generic counterpart (Stack(Of T)) that enables working with a single type in a strongly typed fashion. The Stack collection also exposes the Count property which returns the number of objects that it stores.