Auralex is a company that makes affordable acoustic treatment for any room in which the sound needs to be deadened. As of this writing, Auralex is pretty much a synonym for acoustic treatment. Because reflected sound is inaccurate sound, acoustic treatment keeps rooms from having too much unwanted sound in them for recording/mixing purposes. By controlling what sound is allowed in the room, the sound coming from speakers are going to be truer to what you are looking to hear.

Auralex was founded in 1977 in a garage. At that time acoustic treatment was so expensive that only huge broadcast and recording facilities could afford them.

Note to those with a home studio: Mars Music seems to have some sort of inside track with Auralex. Acoustic panels from there are much less than anywhere else.

note: I do not work for Auralex