The following is a classic pawn breakthrough that creates a passed pawn for the most advanced side. The key things to keep in mind is that this breakthrough will only work for the side that is most advanced and both the breakthrough and defense begin by moving the middle pawn.
White to move and win
1.b6! The breakthrough works for the side that is most advanced, in this case White. 1…cxb6 [1…axb6 2.c6 bxc6 3.a6] 2.a6 This move removes the b7 pawn. 2…bxa6 3.c6 and the c-pawn promotes, because the Black King is too far away to stop it. If Black had the move he could have defended with 1…b6! preventing the breakthrough.