A simultaneous game consists of playing several games at the same time against different opponents on separate chess boards.
How it works ? : I start by playing my move on chessboard 1, and my opponent 1 thinks about his answer. Meanwhile, I play a move on each of the following chessboards, and only when I have gone all the way around and I am back on chessboard 1, does my opponent 1 play his answer. I play the next move and it’s back to one turn !