In these rook-pawn endgames the key rule is that if the defending king reaches the queening square (h8 in this case) then the game is a draw. If the attacking king manages to control it (but not occupy it), however, then it can be a win. You can see this by looking at the key positions
[FEN "7k/8/6KP/8/8/8/8/8 w - - 0 1"]
White cannot stop Black from playing ...Kg8-h8 ad infinitum, and h7 leads to an immediate draw by stalemate. Similarly if
[FEN "7K/5k2/7P/8/8/8/8/8 w - - 0 1"]
This position is also drawn because White cannot extract the king from in front of the pawn.
In the game, Black to play goes ...Kf7, and White cannot stop Black from playing ...Kh8 eventually, reaching the first position. Hence the position is drawn.
If it were White to play in this position, then 1. Kg6 wins. 1...Ke7 2. Kg7! (any other move allows 2...Kf8 and again Black reaches the first position) followed by h4-h5-h6 leads to a promotion that Black cannot stop.