What's the difference between an echo and reverberation? Here's a quick explanation:

An echo is a single reflection of a soundwave off a distance surface. Reverberation is the reflection of sound waves created by the superposition of such echoes.

An echo can only be heard by humans when the distance between the source of the sound and the reflecting body is more than 50 feet in distance. A reverberation can occur when a sound wave is reflected off a nearby surface. 

An echo is usually clear and can be easily distinguished because of the distance and time the sound wave travels. Reverberations do not usually have enough distance or time to travel which means they can pile up on each other making it very difficult to comprehend.

Echoes can be used to determine the distance of a reflecting object such as a large building or mountain if the ambient temperature and humidity are known. Reverberation does not allow enough travel time to use it to measure distance.

With reverberation, sound waves pile on top of each other arriving at the receiver or ear at different times making it difficult to comprehend or understand.

The piling up of soundwaves also increases the sound energy in a room. This buildup of energy eventually will excite the structure and increase the overall volume in a room.

Reverberation in a room will cause people to raise their voices in an attempt to compensate for their inability to understand speech.

Adding sound absorption in a space will reduce the reflections and cause the sound waves to decay at a faster rate. In public spaces, a comfortable decay time should be less than 2 seconds.