Daughter board is one that mounts to the cpu to hold sound simm's etc. Mother board and backplane are the same, The board that mounts on back left lower wall. MM board or enhanced is considered a daughter board. Backplane has all your wires running to it and in old s and s+ terms it was called a mother board. Your cpu,processer, what ever you want to call it slides out of the tray and attaches to the backeplane "motherboard" inside the cpu is the daughter/expansion board--if needed. I could go on for days but that sums it up pretty much.