Echo – Several repetitions of the original sound but at lower and lower volume.
If you have ever been to a canyon and shouted, you will know the effect of echo.
Basic echo looks like the following.
In a canyon an echo is a reflection of sound that arrives at the listener with a delay. The delay is directly proportional to the distance of the reflecting surface from the source. Echo location (sonar) is used to locate items in the air or sea.
Echo is a simple term and it means the same in music as it does normally. Sound waves bouncing off walls produce an echo, but electronic devices in music production can replicate this as well.