Obvious Moves don't always Win
Obvious moves don't alwyas win, even in the most innocent looking position...
Two obvious moves suggest themselves: capturing the b7-pawn or advance the f-pawn...Neither of them works!
If 1.Kxb7 Kb3 2.Kc6 (2.f4 Kc4 3.f5 Kd5 looses the pawn) 2...Kc4 3.Kd6 Kd4 4.f4 Ke4 and Black will win the pawn.
If 1.f4 b5 2.f5 b4 and both sides Queen with a drawn result.
The winning idea is for White to advance his pawn to the Queening square f8, but also move his King to Black's b-pawn's critical squares, c2 or b1.
1.Kd6! Ka3 (1...b5 2.Kc5 Kb3 3.Kxb5 Kc3 4.Kc5 Kd3 5.Kd5 and the pawn is safe)
2.Kc5 Ka4 3.f4 b5 4.f5 b4 5.Kc4! (Necessary, as 5.f6 leads to a draw) 5...b3 6.Kc3! Ka3 7.f6 b2 8.f7 b1/Q 9.f8/Q+ Ka4(9...Ka2 allows 10.Qa8#) 10.Qa8+ Kb5 11.Qb7+ and White wins Black's Queen and the game.