A citation manager can help you collect bibliographic information for the sources you read and use; organizie the PDFs and other documents that go along with the citations; and format in-text citations or footnotes, and bibliographies.
This tool not only formats citations and bibliographies for you, it also helps you stay organized in the paper writing process. Great for undergraduate projects with fewer than 10 sources.
If you know you are going to be working on larger research projects in the future, or you're interested in a more advanced citation manager, then Zotero could be for you.