Many believe that the guitar's developmental beginnings lie in the ancient cultures of Rome, Egypt, and the Near East (Babylonia). Evidence of the existence of guitar-like instruments (such as the arabic Oun) has been found in the artwork of all three cultures, as well as in some of their respective literature. Most of the archeological evidence gathered on the early guitar, or the Lute, seems to suggest that it was originally created as a crude variant of the harpsichord. The guitar's design underwent a great deal of change and improvement before becoming the instrument we know and play today, but many basic aspects of it's design have remained virtually unchanged. Essentially, every guitar has three components, strings, the neck that they are stretched over, and a body for amplification of the sounds they make when plucked, strummed or picked.
The first written mention of the guitar dates from the 14th century. In this account, it was described as having 3 double courses (string pairs) and a single string, which was used to play higher notes. The instrument experienced a surge of enthusiasm and popularity in 16th century Spain, where, due to it's relative lack of expense and portability, it became the preferred instrument of the country's lower and middle classes. Eventually, during the 17th century, a fifth course of strings was added and citizens of other European countries began to develop a level of fondness for the guitar equal to that of the Spanish. From there, the instrument's use slowly began to spread to the colonies of the New World, Central Asia, and to a certain extent, Africa.
During the middle of the 18th century, the instrument took on it's modern form. Guitar makers made the four double courses single and added another, much deeper, sixth string to the mix. The body of the instrument was broadened vertically, made more curvy (earlier models had been somewhat box-like in their shape), and thinned at the waist.The wooden tuning pegs were also given an overhaul, being replaced by a modern, metal machine head.
This model was changed little for the following half-century or so, until, during the 1930s, a handful of musicians and inventors began to experiment with electricity as a means of amplifying the instrument's sound. Most notable among these innovators were Les Paul and one Leo Fender. Les Paul designed quite a few formative prototypes of the electric, but it was fender who perfected those designs and made them commercially viable. For that reason, Fender is now the world's most instantly recognizable, best-selling guitar brand.
Unlike traditional guitars, the electric guitar's sound isn't amplified by reverberations within a hollow wood body. Instead, the vibrations of the steel strings are detected and converted into an electric signal by rectangular magnetic plates called "Pick-ups". From here, the signal is sent to an amplifier, and in turn routed to a speaker, where it is reproduced as sound.