Key squares are the squares from which the stronger side's king forces the pawn through. For a pawn on the fifth rank the key squares are the three in front of it on the sixth, and if the king seizes them the win follows regardless of the opposition.
Here White has the king on e6 and a pawn on f5; Black has the king on f8. White to move, and the position is won (per the tablebases): the king stands in front of the pawn and controls the key squares, so the f5 pawn walks through to queen unimpeded.
Understanding key squares is the foundation of pawn endings: the point is not simply to push the pawn but first to walk the king onto the right squares in front of it.
Drag a piece onto the board, or click a piece and then click the squares. The cross beside the pieces sweeps every piece of that colour off the board, and a single piece can be dragged off the edge.
The pieces will be arranged into the chosen pattern.
It is the mating side to move. Find mate in one.
Openings, endgame positions and breakthrough studies - the set-up appears on the board.
Squares which, once occupied by the king, guarantee the pawn gets through whatever the opponent does. For a pawn on the fifth rank they are the three squares a rank further on, in front of it.
For a pawn up to the fifth rank they are the three squares a rank in front of it. For a pawn on the fifth or beyond, the squares directly in front of it become key as well.
In practice no: the weaker side's king, once it reaches the corner, holds the draw. That makes the edge pawn the hardest of all to convert.
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