The board is an 8-by-8 grid of alternating light and dark squares; files run vertically (a through h, left to right from White's side) and ranks run horizontally (1 through 8, starting from White's back rank). Every square has a fixed color that never changes, which matters for concepts like "good" versus "bad" bishops and opposite-colored-bishop endgames, since each bishop is permanently confined to squares of one color.
Square names are the basis of algebraic notation: a move like Nf3 means "knight moves to the square f3," and a capture like exd5 means "the e-file pawn captures on d5." Central squares (d4, d5, e4, e5) are especially valuable because pieces posted there influence the most other squares on the board, which is why controlling the center is a core opening principle.
Certain squares also acquire strategic importance during a game independent of their board position — key squares in pawn endgames, or an outpost square that an opponent's pawns can no longer attack — and recognizing these squares is central to positional understanding.