You're probably familiar with it by now but, in case you're not, Guitar Hero is a rhythm game where you have to press buttons in rhythm with the music. Songs are all pre-programmed so that you actually feel like you're playing the guitar lines from the song. In World Tour, you get to play the drums as well as the guitar.
Three different types of note fly down the screen, activated by pressing the 4,5 and 6 keys. When playing the drums, you also have to hit the bass drum, which is done by tapping 7, 8, 9 or 0- different keys are quicker to press depending on where your fingers are, so this is useful.