From the TMS admin guide:
A reference is information which can be associated with one or more conferences. A reference can include a reference name, reference code, a comment and contact information. It can be used whenever a conference needs to be associated with a specific code/name/other info.
One use case and example that I can think of, is if you have someone that has a lot of conferences, you can add a reference to all of them so that you can see who the conference is for as well as any other important data for this user that you think should be known.
