What does P K4 mean in chess?

pawn to kingP-K4 which means pawn to king (the e-file) four (whites fourth rank). Then black answers 1…P-K4 which means Pawn to king four (blacks fourth r...

What is diagonally adjacent?

is that adjacent is something that lies next to something else, especially the side of a right triangle that is neither the hypotenuse nor the opposite wh...