What is a Violin?
Most people have seen a violin, but in case you never took a close look or need a quick refresher, here is an overview of the different components.
"Violinconsruction3" by Sotakeit at the English language Wikipedia. Licensed under CC BY-SA 3.0 via Wikimedia Commons.
The violin makes sound through vibrations in the strings which are amplified by the hollow body, and projected out of the f-holes. The pitch of the notes depends on how taught, thick, and long each of the strings are. The violin is tuned by adjusting the tension of the strings through either the tuning pegs on the scroll, or the fine tuners on the tailpiece. Each string has a different thickness giving a range of pitch starting with the thickest (G string) on the left and ending with the thinnest (E string) on the right. Different notes are then played through adjusting the length of the vibrating part of the string. This is done by simply pushing the string down firmly onto the fingerboard at the point that will achieve the desired note.
http://www.learntoplaymusic.com/blog/arco-violin-bowing-technique-play-violin/
A bow is used to make the strings vibrate. The hair, which is made of either horse hair or a synthetic substitute, is dragged perpendicularly across the strings about halfway between the end of the fingerboard and the bridge. The inward curve of the stick serves to tighten the bow hairs when more pressure is applied, allowing the musician to play more loudly with a small amount of downward force.