Imagine the following scenario:

Before driving off in your car, you look up the route to your destination. As you don't have a hands free navigation system you need to keep in mind a visual representation of the map. As you drive along you are updating this representation. That is, you can forget about the parts of the drive you already completed and focus on the upcoming sections of the route.

The capacity to keep and continuously update mental representations of space in your mind is called spatial working memory.