Move numbers and variations

The number that groups one White move and Black's reply within the written record of a game.

A ply is one move by one side, rather than the pair formed by White's move and Black's reply.

In chess notation, three periods after a move number show that the displayed move belongs to Black.

The main line is the central sequence followed continuously while alternatives appear as branches.

A variation is a legal sequence of moves that explores an alternative from a particular position.