As the host of a class/meeting, you can manage participants such as renaming, muting, stopping video and other controls for participants. For more, visit this page.
If somebody joins the room late, or has been kicked out (e.g. due to connectivity), a notification will pop up for you to allow people to join the group.
The participants list also has options for students to give you simple messages:
These appear next to their name in the list. You have a ‘clear all’ button to switch them all off.
Students also have raise hand/lower hand options. A hand will appear on their video.