I used the term “message thread” while helping someone troubleshoot a problem the other day and she was unfamiliar with the term.
A message thread is the back and forth exchange you might find in a messaging or text message thread between two people or a group.
It could also refer to an exchange on one topic in an email when both sides use the “reply” button to go back and forth. The term is also used for exchanges on a topic in a forum or a string of comments and replies on a post. Sometimes that might be called a comment thread.