White noise is a sound frequency. Pure white noise combines all sound frequencies together, with equal values of low frequencies all the way up to very high frequencies. White noise is the most effective at blocking distractions because it covers the largest spectrum range. In additional to helping you sleep better, it's great for reading, writing, studying, or anything else that requires focus. There are other "colors" of sound, too.
Pink noise is blend of high and low frequencies that produce a mesmerizing waterfall effect. Pink noise is great for melting away stress while keeping you alert and energized. The airy pulse creates a therapeutic environment that relaxes your mind and body. Brown noise utilizes the lower sound frequencies to generate a deep ambient rumble. Brown noise is excellent for aiding sleep, pacifying children and pets, soothing migraines, and even masking Tinnitus.
A white noise machine is a device that produces these random frequencies to create a consistent base of backgrounds sounds that mask out disruptive noises. Depending on the brand, white noise machines might produce soothing pink noise sounds like a rushing waterfall or wind blowing through trees, or a whooshing fan. Most modern white noise generators are electronic, usually generating the sound in real-time within audio test equipment, or via electronic playback of a digital audio recording.
In addition to helping you sleep better, sound-masking devices (also called sound machines) can provide privacy. If you work in a cubicle at an office, you can probably overhear your coworkers' talking, typing, using a copy machine, stapling papers, etc. The constant sounds from a white noise machine can mask these annoyances so you hear them less, meaning you can concentrate more on your job. White noise can also give you privacy when talking on the phone so your coworkers can't make out every word you say to your clients, doctor, or when speaking about a personal matter.
The benefits of white noise (and other color noise) have been utilized in clinics, schools, households, and offices around the world. You don't have to buy an expensive white noise machine or sleep machine to enjoy the benefits. And if you travel, many are very compact and portable so you can pack it anywhere.