Significance

From Wikinfo

Significance is the basic process of whether or not something matters, makes a difference, is a real change. An event is significant often because it leads to other changes, opens the door to them, more or less acting as a trigger. In journalism; in addition to who, what, when, where, and how; explaining why an event is significant is often the most important part of a story.

It's like when you look at a picture and something is changed when you are not looking. When you look back is the change striking or barely noticeable? Significant events change the "big picture."