Many of the world's telephone directories include a section in yellow which lists phone numbers for businesses, not people's homes. In some places, it's pink or another color. In America's big cities, there are entire yellow-page books.
Yellow pages are organized by category - from "Abdominal Braces" to "Zoos." Plumbers and restaurants and other businesses pay extra for display advertisements next to their numbers.
These days, yellow-page directories face stiff competition from Internet search engines and online business directories, including "Yelp," whose name reads like a shorthand version of "Yellow Pages."
In 2007, high-tech pioneer Bill Gates predicted that "Yellow Page usage amongst people, say, below 50, will drop to zero, near zero over the next five years."
Things aren't that drastic yet.
But it's clear that young people seeking information about, and reviews of, businesses are leading the migration away from Yellow Pages and toward the Internet and handheld devices.
The printed big book survives, but in some communities you have to request a copy to get one. It isn't plopped onto your front porch once a year as it used to be.
The Associated Press reports that categories in these directories are also changing fast to reflect our times. You won't find "Discos" in the yellow pages any more, or "Drive-in Movie Theaters," "Typewriter Repair," or "Moustache Wax." Now it's "Body Piercing," "Teeth Whitening," "Satellite Equipment" and "Dating Services."
The AP even found a trendy new category in the Richmond, Virginia, Yellow Pages. It's for businesses that organize clients' homes by employing the ancient Chinese art of arranging objects to improve one's fortunes.
The listing: "Feng Shui."