A motherboard is the backbone of most modern computers. It is literally a board, with all of the computer's main tools (hardware) on it, or connected to it, driving the “engine” of your computer. It is where most of your hardware is located. Hardware, like RAM and the CPU, are on the motherboard, or connected to it. All expansion ports are also wired into your motherboard. It is like the engine block--everything driving your computer (or engine) is connected to it to make your car/computer run. Because of the size differences between laptops and desktops, motherboards sizes can vary too, but their basic functionality is the same.