Lists Structures are one way to represent compound information.
They are useful when we know how many pieces of data we wish to compound into one piece. In many cases, however, we don't know how many things we wish to enumerate, and in that case we form a list. A list can be of arbitrary length, that is, it contains a finite, but undetermined pieces of data. Forming lists is something that all of us do. Before we go grocery shopping, we often write down a list of items that we want to purchase.