Not a dumb question at all. The "back" refers to the flip while the numbers refer to the twists. For example, a "back layout with a full twist" could be written just as above, a "back 1/1" or "layout 1/1" or "layout full" or just a "full".
1/2 = half twist
1/1 = full twist
1 1/2 or 3/2 = one and a half twists
2/1 = double twist