Bishops of Opposite Colors
As you already know you and your opponent both start out with two bishops; one on white and the other on Black. Say for example that in the Endgame you end up with a King, a White Bishop, and two Pawns while your opponent has a King and a Black Bishop (Hence the title Bishops of Opposite Colors)! It is incredibly hard to win even with the advantage of having two extra Pawns. The additional Pawns can't really help you in a situation like this so it is better to Draw it. The Kings will be constantly targeted by the Bishops in order to ensure a Draw. In the meantime, while they put you in Check, you can slowly make your way towards your Pawns which will give you a better chance of winning but it can also be risky for you can be trapped and lose the game. I'll demonstrate what I mean with the following "Game." I think it best explains why it is hard to have a decisive victory or even a victory at all. If you or your opponent traps themselves within the Pawn structure they are then unable to come back . Now with this type of situation the "King & Pawn's Game" works the best! To put it simply, use your King to escort your Pawns down while your Pawns protect your King. If their King is able to get within the heart of your Pawn structure it is automatically a Draw because you'll be unable to progress your Pawns and it is impossible to Checkmate somebody with just a King and a Bishop; it is an automatic Draw situation.