In C-Cross, you want to connect two opposing sides of the game board with your own tiles — but before you can place a large C-shaped tile on the board, you need to place three pawns in the area where this tile would go. When you do conquer an area with three of your pawns and cover it with one of your tiles, you return those pawns to your supply. The tricky part, however, is that if your opponent has a pawn in this area when you cover it, you must lose one of your pawns elsewhere on the board, replacing it with the opponent's pawn!
If you connect two opposing sides with your C-tiles, you win. Alternatively, if your opponent can't play, you also win!