(Public domain image from Webster's Dictionary 1911. Larger image)
The guitar is descended from the lute. Guitars usually have 6 strings. A variety of different tunings are used. The most common by far is (low to high) E-A-D-G-B-e, which provides a good compromise providing both simple fingering for many chords, and the ability to play common scales with minimal left hand movement. Others such as E-A-D-F#-B-e (which provides the same intervals as for a lute), or D-G-D-G-B-D ("open G," commonly used for blues or slide guitar) tend to be restricted to more specialist forms of music.
Broadly speaking, guitars can be divided into 4 categories:
- Classical guitars: These are typically strung with nylon or gut, and amplification is provided by the resonant hollow body. They are normally played in a seated position and used to play classical music. Flamenco guitars are almost equal in construction, have a sharper sound, and are used in flamenco.
- Acoustic guitars: Similar to the Classical guitar, but with a reinforced neck to sustain the extra tension of steel strings which produce a louder and brighter tone, the acoustic guitar is a staple in folk, traditional and blues music.
- Electric guitars: Electric guitars have a solid body and produce little sound without amplification. Electromagnetic "pickups" convert the vibration of the steel strings into electric signals which are fed to an amplifier through a cable or radio device. The sound is frequently modified by other electronic devices or natural distortion of valves in the amplifier. The electric guitar is used extensively in blues and rock and roll, and was invented by Les Paul and independently by Leo Fender.
- 12-string guitars usually have steel strings and are widely used in folk music and rock and roll. Rather than having only six strings, the 12-string guitar has (logically enough) twelve. Each pair of strings is tuned either in unison (the two highest) or an octave apart (the others). They are made both in acoustic and electric forms.
Hybrids of acoustic and electric guitars are also common. There are also more exotic varieties, such as "double-headed" electric guitars, all manner of alternate string arrangements, and such.