Some say one should use more than one cutting boards because if you use just one board for raw meat and vegetables, bacteria from raw meat moves to the board and then to the vegetables, then you eat that vegetable raw, and you get sick.
Some uses more than two cutting boards: one for fish, another for raw poultry, yet another for dairy and so on.
What if I use just two rather than 3 or more? One for stuff to be heated, another for everything else. What do I gain by using 3 or more rather than 2?