Makey Makey works just like a USB keyboard or mouse, sending keyboard (WASD, spacebar, etc) and mouse (left click, right click, etc) signals to your computer. The Makey Makey circuit board works by opening and closing circuits, just like any other button. Instead of the circuit being closed underneath your keyboard, the circuit is closed through the conductive objects you connect with alligator clips like your hand or your lunch or some tinfoil. When the circuit is closed, the Makey Makey sends a command to your computer, just like when a button is pressed on a keyboard.
SESC's Makey Makey classroom kit includes 14 circuit boards and activity supplies.