The Timeline is where you can post announcements to everyone enrolled in the course — a reminder about an upcoming session, a heads-up about homework, anything the whole class or a student's family should see.

Depending on how your institute has configured the course, learners may be able to comment on your posts, or commenting may be turned off. Either way, the Timeline is meant for course-wide updates rather than one-to-one conversations — for anything private to a single student or parent, use Chats instead (see Chatting with students, parents, and admins).