The [] are just delimiters to indicate everything written between them describes a single move. A dash - means continuation, and separates the various 'legs' of the move, a question mark indicates the continuation is optional, and that what was written before it is a valid move in itself. So [F-sF] means an F move mandatorily followed by another F move in the sideway direction (i.e. perpendicular to the first). By default non-final legs must go to empty squares, and continuation legs go as much as possible in the same direction.
The [] are just delimiters to indicate everything written between them describes a single move. A dash - means continuation, and separates the various 'legs' of the move, a question mark indicates the continuation is optional, and that what was written before it is a valid move in itself. So [F-sF] means an F move mandatorily followed by another F move in the sideway direction (i.e. perpendicular to the first). By default non-final legs must go to empty squares, and continuation legs go as much as possible in the same direction.