It even has guitar controllers which have 5 buttons, each in place of the first five frets of varying colors, a little switch thing where the strings would be and a whammy bar.
(http://img144.imageshack.us/img144/163/guitar20heroof1.gif)
The game itself, is you are in a cover band and you play a whole bunch of different songs. In the center of the screen is a guitar fretboard which is always scrolling towards you. On it are the different buttons you've got to hit just like all the other, match the beat games, but when you miss, the guitar part you missed is muted from the song. For instance imagine Iron Man (I) without the long notes in the beginning, or in Free Bird (II) during the solo missing every third note. When you screw up part of a song, you know it. Each game has about 40 to 50 songs on it.
(http://img144.imageshack.us/img144/5792/guitarhero0024iq9.jpg) (http://img144.imageshack.us/img144/7965/guitarhero2xd9.jpg)