String instruments are those which make notes by vibrating. The best examples are the guitar, violin, piano etc. To play them, one has to make the strings vibrate by striking, plucking or rubbing a bow against them.
Generally, string instruments have something called a sound box or resonator, which amplifies the sound. Each of them, however, works in their own way. For example, a guitar produces sound when the player plucks the string, either using a finger, or a piece of plastic called plectrum. The length of the string is fixed, and controlled by the player himself.
There are different factors influencing sound in a string instrument, and the most important ones are length, weight, and tightness. If the strings are long, the vibration created would be slower, making lower sounding notes.
