This is where the sound wave interacts with a surface and bounces off. The one reflection that most people are aware of is an echo. In a theatre or studio we try to minimise reflections at much as possible so as to achieve a pure sound.
As with absorption soft material tend to be good a reducing reflection, there are many specialised companies who produce sound proofing product for use within studios. Within a theatre setting it is more effective to use Sound Absorping drapes http://acousticsfreq.com/sound-control-acoustic-curtain/
Diffusion also comes into play with reflections. With this though reflections are occurring the refleced wave is split into more than one path way. As seen in the image above, again there are many available commercial types of diffuser to help with this issue within the studio.
Matt Cooper 