how many strings guitar have?
how guitar projects sound?
what are different types of guitar?

A typical guitar have 6 strings but there are other guitars (bass guitar) which have 4-6 strings.
The sound of the guitar is projected either acoustically, by means of a resonant chamber on the instrument, or amplified by an electronic pickup and an amplifier.
There are three main types of modern guitar, the classical guitar, the steel string acoustic guitar or electric guitar, and the Hawaiian guitar which is played across player's lap.