An acoustic guitar is a guitar that produces sound acoustically by transmitting the vibration of the strings to the air as opposed to relying on electronic amplification (see electric guitar). The sound waves from the strings of an acoustic guitar resonate through the guitar's body, creating sound. This typically involves the use of a sound board and a sound box to strengthen the vibrations of the strings.
An electric guitar is a fretted string instrument that uses a pickup to convert the vibration of its strings which are typically made of steel, and which occurs when a guitarist strums, plucks or fingerpicks the strings into electrical signals. The vibrations of the strings are sensed by a pickup, of which the most common type is the magnetic pickup, which uses the principle of direct electromagnetic induction. The signal generated by an electric guitar is too weak to drive a loudspeaker, so it is plugged into a guitar amplifier before being sent to a loudspeaker, which makes a sound loud enough to hear.