The Guitar

I will now teach you about the guitar. I would like to start with a basic knowledge of sound. If you don't already know, sound is simply vibrations in the molecules around us. Those vibrations once picked up by the ear drums are translated into our sense of sound. A guitar works because the strings vibrate when plucked. This vibrations resonate differently depending on which string is plucked and which frets are held. This is why the guitar makes any sound at all. The hole in in an acoustic guitar is used to get more bass out of the instrument. That's about all there is to know about the acoustic guitar.

For a more in-depth analysis: http://www.phys.unsw.edu.au/music/guitar/guitarintro.html