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When you search a random topic, Wikipedia is usually the first hit you get. This might be why 374 million people visit Wikipedia each month. And yet, Wikipedia, run by a nonprofit organization, makes no money, unless you donate to the site.

Wikipedia turns 15 today. And it has helped change the research world. The Encyclopaedia Britannica stopped printing actual books in 2012, after being in print for 244 years. Now if you want to look something up in the encyclopedia, you have to log on to Britannica's website.