Guitars have been around for 4,000 years, evolving from early bowl harps. Guitars are categorized as string instruments and are divided into two groups: acoustic and electric. Acoustic guitars work without electric inputs that amplify the music, instead using a cut out in the middle of the guitar's body to project the music. Acoustic guitars include the classical guitar, which uses thick nylon strings, the steel-string guitar, and the archtop guitar, which is most closely associated with the bowl harps of old. Electric guitars use inputs to connect to amplifiers, which allow the sound of the guitar to be changed and shaped by the amplifier itself, or a host of pedals and effects. Guitars have been pivotal in defining many genres of music, most notably rock and roll, folk, flamenco, and blues. They are also used in jazz, bluegrass, country, and soul music to add depth to other instruments which take center stage in those genres. How Is This Passage Oragnized Thanks!!!