Each square has a name

The board is a coordinate grid. The eight columns are files, labelled a to h from White's left. The eight rows are ranks, numbered 1 to 8 from White's side. A square is named file then rank, so e4 is the e-file, 4th rank.

This is the ordered pair $(x, y)$ from a graph: the file is the x-coordinate, the rank is the y-coordinate. A name gives you a position, and a position gives you a name. Because the file and rank are chosen independently, there are $8 \times 8 = 64$ squares, one for each pair.