Known as the GIOP, general input/output pins, is located along the top of a Raspberry Pi; there is a total of 40 pins on each pi. You can do numerous things with the GIOP such as program it using Scratch, where you can operate buttons and LEDs.
While its very simple to connect components to the GIOP, you have to make sure things like LEDs have resistors to limit the current passing through it. You should also be careful when trying to connect motors, you have to use the H-bridge circuit to connect to the Raspberry Pi.