Random-type noises, called "White Noises" as a category, help people sleep, rest, and mask unwanted sounds.
While collectively called "White Noises", selecting different frequency characteristics results in colored noises. The most common of these are white, pink, and brown noises. These are all produced by massaging random noise across the sound spectrum.
White noise is broadly spread across the sound spectrum, including low-frequency, mid-range, and high-frequency sounds. It can be compared to the sound of an old-style radio tuned between stations or an old-style television tuned to a station that is off-the air for the day. Many people find this type of noise a bit harsh, though it has been helpful for some sufferers of tinnitus (or "ringing in the ears").
Pink noise is louder at the low-frequency end of the spectrum, and softer at the high end. The sound of  light to medium rainfall is an example of real-world pink noise. Most people find this noise very calming and pleasant.
Brown noise is even deeper, even stronger at the low end, and without the high frequency sounds of white and pink noises. It can sound similar to air flowing through a large duct. This is also generally perceived as pleasant.