recently i have been studying how many sqaures there are on an 8x8 chessboard and now extension work is to study how many rectangles there are are on an 8x8 chessboard

i have worked out that there are 1296 rectangles and now i am trying to find a formula for it. i have researched on some other websites and they say that (9c2)(9c2)=1296 i understand why it is 9 (because there are 9 horizontal/vertical lines) but i don't understand why it is 'c2' could someone please explain?

thanks very much