Types of a Guitar

Acoustic Guitars - There are several notablesub categories within the acoustic guitar group: classical and flamenco guitars; steel-string guitars, which include the flap-topped, or "folk," guitar; twelve-string guitars; and the arched top guitar. The acoustic guitar group also includes unamplified guitars designed to play in different registers, such as acoustic bass guitar, which has a similar tuning to that of the electric bass guitar.

Electric Guitars - can have solid, semi-hollow, or hollow bodies, and produce little sound amplification. Electromagnetic pickups convert the vibration of the steel strings into signals, which are fed to an amplifier through a cable or radio radio transmitter. 

Ukelele - is originated in the 19th century as a Hawaiian interpretation of the cavauinho or braguinha and the rajao, small guitar-like instruments taken to Hawaii by Portuguese immigrants. The tone and volume of the instrument varies with size and construction. Ukeleles commonly come in four sizes: soprano, concert, tenor, and baritone.

And many more types of guitars, you can see it here: http://en.wikipedia.org/wiki/Guitar#Electric_guitars all the types of a guitar.