A "discussion thread" refers to a conversation or series of messages that occur in an online forum or platform. It's an organized way for people to have discussions, ask questions, and share their opinions on a particular topic. Full definition
For example; participants can engage one another in discussion threads about their learning experience as they go through a course. (elearningindustry.com)
Once you're a member, you can initiate new discussion threads for others to join. (theladders.com)
They also submitted screenshots of discussion threads and feedback that they provided students. (citejournal.org)