"Don't call us. We'll call you."
Changes are always happening around us. However, we don't care for all of them. But we do for some and we would like to know whether something has changed in our area of interest. The same is the case with software development. Think of the following situation:
A new entry is added/deleted to a collection or some elements are moved inside the collection. All views that are attached (also known as binded) to that collection need to be notified that something has changed, so that they can adjust.
This process of sharing news that something has happened is called notification