The guitar is a plucked string instrument, usually played with fingers or a pick. The guitar consists of a body with a rigid neck to which the strings, generally six in number, are attached. The bass guitar has largely replaced the double bass and is normally a four stringed instrument tuned one octave lower than the four lowest guitar strings.
Guitars are traditionally constructed of various woods and were strung with animal gut but more recently with nylon or steel strings. Modern guitars can be made of polycarbonate materials.
Guitars are made and repaired by luthiers.
I have been playing and modifying guitars for many years but I am not a professional luthier. Anything presented here has worked for me but is not guaranteed to work for you so take care as it is easy to damage an expensive instrument.