Almost every search you do on the Internet will include a Wikipedia article. While these articles can be informative, they are generally considered unacceptable as sources for college level research. The primary reason for this is that Wikipedia articles are anonymous so there is no way to verify the authority of the creator of the article. And while the quality of articles is generally good, this quality can vary widely. Finally, since all editing is done by volunteers, there is no overall editorial control or systematic fact checking. To understand why this is important, you can read the brief article The Invention of the Brazilian Aardvark.
This does not mean that Wikipedia is not useful! The higher quality articles written for Wikipedia provide extensive lists of references at the end. Most of these references are from authoritative and verifiable sources and are often linked to those sources. So you can use the article itself for general information on a topic (but not a cited source for your paper) and then check the references for additional sources that you might be able to use as cited sources. In other words, while the article itself might not be an acceptable source, it can often lead you to other sources.