Question

explain reverberation

Answer 1

A reverberation, or reverb, is created when a sound or signal is reflected causing a large number of 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.

Answer 2

When we are in open space and [suppose] we shouted the word "ahah"
And in that open place there are a lot of mountains so far in that region.
So when the sound comes back it mix up and makes that "ahah" sound like 6 to 100 people are shouting.