User Summary

The Guitar Hero controller is a guitar shaped controller. It features five colored buttons on the fret, a strum bar, and a whammy bar.

Different types of controllers where made with the different games and where based on real guitars.

Wiki Summary
A guitar controller is a video game controller designed to simulate the playing of the guitar, a string musical instrument. Guitar controllers are often used for music games such as UmJammer Lammy: NOW!, GuitarFreaks, Guitar Hero, and the Rock Band series. The controllers are played by holding down a colored fret button that matches a colored, on-screen note, while pressing the strum bar as the note passes through the target. The controllers also feature a whammy bar, which is used to bend notes and collect each game's equivalent of bonus energy. Different games and models of controllers have introduced additional features, such as effects switches, additional fret buttons, and fret touch pads. The fret buttons are colored usually in the order of (from lowest to highest pitch) green, red, yellow, blue, and orange.

Source: Wikipedia, "Guitar controller", available under the CC-BY-SA License.