The Name Guitar
The English word "guitar" comes from the Spanish word guitarra. Prior to that, it likely was formed from the Latin word "cithara" and an ancient Sanskrit "tar", which meant string.
Baroque Guitar
One of the predecessors to the modern day classical guitar was the Baroque guitar. It was played during the European Renaissance in the 1600s. The Baroque guitar had 9 or 10 strings with 2 strings generally tuned to the same course or note. A lower E string was added later as the form moved toward the modern guitar.
Antonio Torres Jurado
In the 1800s Antonio Torres Jurado started building guitars in a similar fashion to the modern classical and acoustic guitars. Most of today's guitars are derivatives, or alterations, of guitars that Torres designed and built. He is often called the Stradivari of guitars (Antonio Stradivari being the world famous violin maker).
Electric Guitar
The electric guitar was invented in the United States in the 1930s. The first patent for the electric guitar was awarded to George Beauchamp for a guitar he made with partner Adolph Rickenbacker in 1931. A lot of other inventors and guitar makers were working on electric guitars at the same time. Famous electric guitar makers included Les Paul who pioneered the solid body guitar made by Gibson Guitars.
In 1951 Leo Fender invented the Fender Telecaster. This guitar, together with the Gibson Les Paul, the Fender Telecaster, and the Gibson SG would make solid-body electric guitars hugely popular. These are still the most popular styles and models made today.