The bass guitar was created as a happy medium between the electric guitar and the double bass. The major reason that it developed from the acoustic double bass was that it was easier to project to larger amounts of people through the electrical capabilities of a pickup and amplifiers. It is also easier to record sound with. Even though the electric bass guitar has become the more common bass guitar played, the musical genres of jazz, bluegrass, traditional blues, and classical music still tend to use the upright or double bass guitar.
The bass guitar consists of a body made of wood or some other synthetic variation, the neck that is usually covered in frets, and 4 strings. Bass guitars were originally made with 4 strings, but as the musical importance of the bass has improved so have some of the more advanced versions of the guitar. There are now 5-string bass guitars, which add an additional lower string, and then a 6-string bass, which places a higher string on the other end. There are also 8-string bases with the 4 common noted strings and then 4 strings right next to them that are an octave higher, giving 4 pairs of strings that you can choose to play at the same time to get a fuller sound. You can also choose to have a bass without frets. These electric bass guitars are uncommon and are usually used in the jazz-fusion musical genre.