White noise is a random sound signal that borrows its name from white light. When listening to white noise, a random sound is distributed over the frequency domains of audible tones to the human ear similar to the way the eye’s three color receptors get equally stimulated in the presence of white light.  Read a more scientific description from the wikipedia website.

Used in electronic music, white noise is used as a filter to generate other sounds or can be used in audio synthesis to refine the content of high density sounds like cymbals.

White noise is also used in tinnitus masking to help individuals with the ringing-in-ear disorder retrain their ears off the ringing.

 White noise has a modulated variant called pink sound, and has been utilized in the development of some Hemi-Sync brain entrainment programs to create a more natural sound.