The Guitar Headstock

The head stock of a guitar is shown in the figure below.

The head stock of the guitar acts as a mounting platform for the tuning pegs. The head stock comes in different shapes and sizes but serves the same purpose of holding the tuning keys or tuning pegs. The diagram below shows the tuning pegs clearly.

The function of tuning pegs is to tune the guitar strings and keep the same in tune for a period of time. The better the tuning pegs, the better will be the tuning stability. The tuning pegs basically work on a gear mechanism. When you rotate the head of the tuning pegs with your hand, the small spindle through the hole of which the strings pass ( see the above figure), gets a rotary motion through the gear system and the strings starts getting wound over the spindle. 

Many beginners while buying a new guitar do not seriously consider the tuning pegs. But let me tell you that if the tuning capacity of a guitar is not good, the guitar is not worth playing. If you get bad quality tuning pegs, you will get frustrated while always tuning your guitar. This is not the dangerous part. The dangerous part is, as a beginner if you start playing an untuned guitar, you will develop a bad ear. You will not be able to identify chords, scales and many other things because up to that time you would have trained your ears to identify wrong frequencies. If your guitar has tuning problem, go to a guitar shop and get your tuning keys changed with a new set of good quality tuning pegs. 

While buying a new guitar, try to rotate the tuning pegs and see if they are smooth or not. If they are not smooth please never buy that one. Next thing, tune the guitar and bend one of the strings as much as you can somewhere around the twelfth fret and again check the tuning. Check if there is any deviation. If there is any, you know what you need to do.