Quads is a tennis format for doubles.
You have four players, A, B, C, and D.
A & B play eight games with C & D. During those eight games, each of the four players serves one game. After the first four games are played, the pairs switch sides and and play four more games, serving from the opposite side. After the first eight games are completed, the pairings switch. A plays with C, B plays with D. Those teams play eight games, following the previous format. Then one last switch with A playing with D, and B playing with C. Eight more games. Each individual player keeps track of her or his wins during the 24 game match.