amphitheater an acoustic guitar can often be heard with no amplification. In most other performance scenarios amplification is required for the audience to be able to hearthe guitar well. An acoustic guitar can be amplified by placing an amplified microphone near (possibly within several inches) the soundhole of the guitar or by installing an electric pickup in the guitar. An acoustic guitar with an installed electric pickup is not considered an electric guitar.

When we refer to acoustic guitars, we usually think of the 'flat top' guitar, with a distinctive soundhole. They are usually bigger than classical guitars (described below), and feature a somewhat thinner neck and metal (steel) strings. They come in a variety of sizes, from the smaller 'parlour' and 'concert' sizes, to the larger 'dreadnought' and 'jumbo' sizes with the most typical being the 'dreadnought'. They have a distinctive warm (although sometimes metallic) sound and can be strummed for playing rhythm in a wide range of popular music genres, including country, pop and rock, or played 'fingerstyle' for country blues, ragtime and folk. A plectrum or 'pick' can be used, for instance in the bluegrass 'flatpicking' style.

Unlike the electric guitar, the traditional acoustic guitar is not dependent on any external device for amplification. The shape and resonance of the guitar itself creates acoustic amplification. However, the unamplified guitar is not a loud instrument; that is, it cannot "compete" with other instruments commonly found in bands and orchestras, in terms of sheer audible volume. Many acoustic guitars are available today with built-in electronics to enable amplification.

Electric guitars

The electric guitar is the workhorse of rock music, but has its uses in other genres such as blues, jazz and pop music. While an acoustic guitar can be played right off the rack, an electric guitar requires amplification (It is possible to hear an electric guitar without amplification for the purposes of practicing, but it will be much quieter than an acoustic guitar, and electric guitars are never played this way in performances.) The sound of an amplified electric guitar is very different from that of an acoustic guitar, even when no effects or distortion are used - the pickups and amplifier define the guitar's sound to a large extent. Like the acoustic guitar, the electric guitar has a poor sustain. However, amplification and especially overdrive will increase the apparent sustain, and feedback can allow a note to be sustained indefinitely, even for several minutes.

Many people who play the electric guitar wish to use the distortion and other effects. This is covered in more detail in Anatomy of a Guitar.

Technically speaking an electric guitar is any guitar with an electromagnetic pickup to amplify the sound created by the vibration of the strings. Electric guitars come in a variety of shapes and sizes which are not always limited to the acoustical qualities of the shapes and thus can be more comfortable to play. Electric guitars are typically easier to play since the strings usually are much thinner (the strings do not have to resonate as much as with an acoustic), and are closer to the neck, requiring less force to press them down. The multitude of variations amongst these guitars allow them to have a vast variety of different tones. The two most popular basic shapes of electric guitar are the Stratocaster style and the Les Paul style. Most electric guitars that are solid body create very little sound on their own and therefore require an amplifier for all performance purposes.

Solid Body guitars

The typical electric guitar is a solid body guitar. They are called solid body because they are made from one solid piece of wood (or several pieces of wood glued together) and have no soundhole or obvious body cavities. With no apparent soundhole to project the sound they make very little sound on their own and therefore require an amplifier for all performance purposes. It has to have an amplifier not like other guitars. With out it, it would not be loud and make an odd sound..

Archtop Guitars

An archtop guitar is typically a hollow body acoustic or electric guitar which uses steel strings and has an arched top which creates unique resonance. The hollow body archtop is a guitar whose form is much like that of a mandolin or violin family instrument in that the body of the guitar is hollow. Archtop guitars may be acoustic or electric and can look very similar, the only certainly distinguishing feature being an electromagnetic pickup. Some solid body electric guitars are also considered archtop guitars based strictly on their body shape which includes an arched top although usually 'Archtop guitar' refers to the hollow body form. Archtop guitars have been particularly popular in jazz music, usually using thicker strings than acoustic guitars(the thicker strings add tone). These are often louder than a typical dreadnought acoustic guitar. The electric hollow body archtop guitar has a distinct sound among electric guitars.