The reason it's important: if you have more territory, you also possess more room in which to move around.
- the side with less space should initiate exchanges so that he will have more room in which to move around.
- alternatively, the side with more space should avoid exchanges and instead focus on increasing the space advantage.
However, there is a "dark side of space"
- the further a pawn advances the less space it can potentially control
- in closed positions with locked centers you must attempt to get open lines on the wings by breaking with pawns