Use the Classlist tool to view who's enrolled in your course, check users' online statuses, send email or pager messages, view shared locker files, and read their blogs if they have one. You can also use the Classlist tool to change user account settings, and send users a password reset link.
The Online Status icon displays beside the names of other users who are currently online.
Links:
[1] http://staging.docs.d2l/en/accessing-classlist
[2] http://staging.docs.d2l/en/using-classlist
[3] http://staging.docs.d2l/en/taxonomy/term/3