Guitar is one of those instruments that come in various shapes. For instance, the classical or Spanish guitar has a characteristic figure-of-eight shape and is approximately 19 inches long. The sound-box is flat with a bridge toward the base in the lower half, and the sound hole is in the top half. The sides are rather deep. The back is sometimes flat, but in most cases slightly curved. The neck is wide, has up to 20 metal frets, and is around two feet long. The pegbox bends slightly backward. The tuning pegs are attached to the side of the pegbox, with three strings on each side in a six-string guitar. Originally, the guitar was strung with catgut, but modern guitars are strung with metal or nylon strings.

In the classical playing position the player is seated, with the instrument held in front of the body, the neck pointing up at an angle, and the left foot hereby resting on a special footrest. The instrument is plucked with the fingers. The vibration length of the strings can be adjusted with a so-called capo tasto (a clamp) on the neck.

The guitar is native to the Iberian Peninsula. Originally, the guitar was a folk instrument and the vihuela de mano an instrument played by and for the nobility. The vihuela de mano was a kind of compromise between the guitar and the lute. It had the shape and size of a guitar, but the tuning resembled that of the lute, as did the stringing, which consisted of four double-strings. A fifth pair of strings was attached to the bass side in the course of the seventeenth century. The shape deviated slightly from that of the modern guitar. The sound box was smaller and deeper and the waist less pronounced. The sound hole was covered with a rosette.

In the mid-eighteenth century, the guitar assumed greater importance in music elsewhere in Europe. The reason for this was that the lute had gradually been supplanted by the harpsichord. The unmanageability and fragility of the lute (particularly when it came to tuning) contributed to its decline. When the stringing was reduced to six, making it suitable for playing by amateur musicians, its popularity rapidly increased. The new, simplified string arrangement was accompanied by an enlargement of the sound box, which was changed to its present shape. The rosette over the sound hole disappeared as well. This gave the guitar greater volume, aided by the deep body of the instrument. A solo guitar can be heard clearly everywhere in a large concert hall, while a harpsichord, heard from far away, is usually experienced as a faint tinkling.

In contemporary time, there are as many as seventeen types of guitars. But it is the electric guitar that is widely used in world music, especially in music like rock.