Sound reflections happen when sound waves bounce off the wall, or objects, and reflect back. There are two types of reflections: Reverb and Echo (Delay). It is crucial that you understand the difference between these reflections.
In nature, we often hear both Reverb and Echo at the same time. This is why it can be confusing when we isolate one effect.
An Echo, or Delay, is a repetition of sound. It is a series of sounds. A sound source is created and reflected at different distances, resulting in different times. Echo needs distance. Multiple Echos will rarely occur in small rooms.
Reverberation is a prolongation of sound. It is the summation of all the sound in the room. A sound source is created and reflected all over. Those reflections sound like a sustain, not a repetition.