In assessing a position, more advanced players often comment on colour weakness, which usually means that one side has less control over a certain square colour due to his or her pawn structure or piece placement. The following gif illustrates two crucial ideas following the realisation that your opponent has weakened a particular square colour: 1) the idea of using the weakened squares as an outpost (in this case the b5/c4/d5 squares for the knight), and 2) exchanging pieces that threaten to challenge the outpost (in this case the white-square bishops). In order to consolidate his hold on the white squares, White sets up a bishop exchange, followed by taking possession of the outposts.
The original position comes from a game by Petrosian that I have been unable to locate. I’ll update this post once I manage to do so.