Sparse approximation

Sparse approximation is a way of representing a complex thing with only a few pieces of information. Imagine a big circle drawn with a lot of different lines connecting different points. If you want to represent this big circle with only a few pieces of information, you could use sparse approximation. You'd look for the most important lines connecting the points and just draw those lines. That way, you have a simpler version of the circle that's still recognizable but uses much less information.