Wikipedia?
You already know how helpful it is to get some background information on your research topics. Wikipedia is often the default because it's so easy to find an entry. It is literally at the top of most search results on the web.
That said, a wikipedia entry is only as good as the sources it cites and the content can be changed by anyone who creates an account. For that reason, you should not cite Wikipedia, but you can follow the source notes.
For your research papers, we suggest that you browse or search some of the library's online subject encyclopedias. Admittedly, they are not as easy to search, but the quality of the entries is usually worth the effort. In addition, the entries are signed by the author and include the citation.