Reverberation, in psychoacoustics and acoustics, is a persistence of sound after the sound is produced.[1] A reverberation, or reverb, is created when a sound or signal is reflected causing numerous reflections to build up and then decay as the sound is absorbed by the surfaces of objects in the space – which could include furniture, people, and air.[2] This is most noticeable when the sound source stops but the reflections continue, decreasing in amplitude, until they reach zero amplitude.
source: Wikipedia