A main distribution frame is like a giant switchboard where all the telephone cables in a building or area connect together. Imagine that you have a bunch of toy cars and you want to make them go down a big road. You need a place where all the roads meet and connect together so that the cars can go where they need to go. That's what a main distribution frame does for phone cables. It connects all the cables together so that people can make phone calls and access the internet. Without the main distribution frame, there would be chaos and the phone and internet wouldn't work very well.