Guitar are made  up of wood, metal, plastic and electronics. All guitars may be little bit different but have 3 fundamental parts in common. These are: head-stock, neck and body. We’ll discuss about parts of 3 types of guitars. Those are:
1. Acoustic guitars
2. Electric guitars
3. Classical guitars

Acoustic guitar:

1. Headstock:
 It is the part which is at top of the guitar, where tuning things are placed. The headstock in acoustic guitar is simple unlike in most of the electric guitars. Electric guitars have cool design to give it a unique look.
The headstock have tuning keys, tuning pegs and nut.
A. Tuning keys
Tuning keys are the things which are used to tune a guitar. They are associated with gear whichs rotates the tuning pegs to tune guitar. These keys are roatated according to the note wheater to make it sharper or flatter. 
B. Tuning pegs
Tuning pegs are the part where free end of string is inserted and rotated with the help of tuning keys. They rotate as they are connected to tuning keys by simple gear mechanism.
C. Nut
This is the part where string stay before going to the tuning pegs. It usually have shallow grooves for the strings so that the strings are intact in place.
2. Neck
It is the part which is at middle of the guitar where frets are placed. It connects body and the headstock. The strings run through the neck. Small wire bumps are place called frets. These frets are placed such a way that chromatic scale is naturally present.
The neck consists of fretboard, trussrrod frets, and fretlockers. The neck is made up of Rosewood, Maple, Ebony etc. 
A. Fretboard
It is the wooden part made usually up of maple, rosewood or basswood. It is the place where all notes are present.
B. Frets
These are verticle bumps made up of wire which are placed on a distance so that chromatic scale is precisely placed. It acts as anchor to string so that specefic notes can be played on the fretboared.
C. Fretlockers
These are the marks (usually dots, boxes and other charecter or may be absent). These help to track finger in fretboard.
D. Trussrod
The neck bends due to the tension of the strings, so the strings get lifted making very difficult to play the instrument for the longer period. So a metal rod is placed inside the neck so that neck won’t bend due to tension of string and the instrument lasts for longer time.
3. Body
Body of the guitar is a large part at the bottom. It has very important function on getting sound of the guitar. It consists of sound hole, pick guard, saddle, bridge, bridge pins and strap buttons.
A. Sound hole
It is the round opening in the body of the guitar (sometimes there are multiple small holes, f holes or other fancy openings). It lets the air inside the body to resonate and produce the sound of guitar.
B. Pick guard
Sometimes the guitar may contain plastic design below the sound hole. It protects from the picks during playing so that the guitar doesn’t get scratches and other injury.
C. Saddle
It is mostly made up of plastic or bone and elevates the level of strings before they go to nut and tuning pegs. It helps maintaining the height of strings.
D. Bridge
A bridge is a device that supports the strings. The bottom part of the strings are placed on bridge and locked with the help of bridge pins. The top part of the string goes to tuning peg. Usually it is glued with the body of guitar and made up of wood.
E. Bridge pins
Bridge pins are the small pins that help to anchor the sting to the bridge. The bottom part of string is inserted on the holes of the bridge and locked with the help of bridge pins.
F. Strap buttons
These are made up of metal and help to place the strap. The opening of the strap are Inserted to these so that you can carry the guitar. They help the player to play during standing.
G. Cutaway
It is the c shaped cut on the lower part of the body. It helps the player to reach on higher notes and makes easier to play them.

Electric Guitars

The headstock and neck of the electric guitar is very similar in terms of structure and functionality. But the headstock of electric guitar may have interesting design and nice appearance. Also the neck is little bit longer and have higher number of frets. So, electric guitars can hit higher notes. So what makes electric guitar different than acoustic is the electronics used.