Four-in-a-row (or four-in-a-line) is the name for several games in which the object is to line up four things in a row. The board is arranged with empty spaces. You and your opponent take turns placing your pieces in those spaces in an effort to connect four of your own pieces in a row. Once your piece is placed, you can't move it. You win when you get your line of four, but if no one ends up with a line, the game is a tie.