Participants in Teams meetings can use the meeting chat to discuss topics, post pointers, and so on. The access rules are changing for some added to a meeting to make sure that people don’t get too much access to meeting resources (like chat) once the meeting finishes. It’s a small but important point for Teams administrators to understand.
https://office365itpros.com/2020/11/24/new-access-rules-teams-meeting-chat-membership/
