For example, White could try 1.Bf4 on his first move, with the idea 1...Bxa2 2.Bxd6 and 3.Bxa3 is a draw, but Black can defeat this idea with 1...Bxf4 2.Rxa3 Bc2, which wins. To understand why one move works and another one does not, requires quite advanced chess knowledge. Indeed, it will not be obvious to many players that the position at the end of the given line (second diagram) is a draw at all.