The workshop materials below use Version 2 of Overleaf, which is part of our Yale subscription. Overleaf merged with ShareLaTeX, and the new platform looks like ShareLaTeX with a green color scheme and some of Overleaf's coveted features.
The example below show how to use the basic cite regime, BibTeX and natbib (the former included in LaTeX by default, the latter a package), and two newer tools — biblatex and biber. BibTeX and natbib haven't been updated in a while. As of the second version of biblatex, biber is the official .bib file parser — not BibTeX — so the .bib file is quickly becoming disassociated from the specific package behind it.
The workshop the materials come from operates on the assumption that the majority of your research writing requires a knowledge of BibTeX and natbib, but my goal is to also inform you about the future of citing in LaTeX.
A .bib file is still the preferred method for providing information about your references to biber.
Why are the session examples in ShareLaTeX instead of Overleaf? There are several different online LaTeX editing tools, including Overleaf and Authorea. Yale has an institutional subscription to Overleaf.
Authorea is a different type of tool, and it focuses more on collaborative writing with the goal of submitting papers. It goes beyond just LaTeX, has some pretty cool features, and its UI is easy to use if you are collaborating with non-LaTeX users. However, Authorea has a cap on the number of documents you can keep private, so if you're looking for a place to keep your private collaborative course notes, your private research diary, a private scratchspace for hobbies you have (such as conlanging; LaTeX handles them fabulously), and write papers for submission, Authorea is not the right tool for you.