Hi Christine,
Good question. Resin generally refers to the two-part systems which when mixed together will harden. (UV resin is a bit of an exception here, but I digress).
When people refer to resin, they are most likely referring to epoxy resin, which is a kind of resin. There are other kinds, however, that you may come across. I detail them here:
https://www.resinobsession.com/resin-frequently-asked-questions/what-are-the-different-types-of-resin