The term Yellow Pages refers to a telephone directory of businesses, categorized according to the product or service provided.

AND

Wikipedia (pronounced /ˌwiːkiˈpiːdiə/ or /ˌwɪkiˈpiːdiə/) is a multilingual, Web-based, free content encyclopedia project.

Both list products and services but with the online yellowpages, you the consumer are directed where to buy those products and services usually with a great company description as well as an outline of when, where and how you can attain them. Both are great resources and can be used to any online visitors credit!