This will help to keep your meeting from accidentally being hijacked by your students, or crashing for you and your students because there are too many webcams active in the meeting. You can always allow meeting participants to "unmute" themselves as needed once you have started your Zoom meeting.
Nonverbal feedback in Zoom allows your students to: raise/lower their hand, respond "yes/no," ask to go slower/faster, agree/disagree, clap, and more. This tool is most useful for quickly gauging how your students are responding to a particular concept or question (e.g., "can you all hear me?" or "Are there any questions before we go on?"). You will be able to see a number above each feedback icon in the participants list to see how many students gave a particular response and you can reset all responses as needed. Learn more about Nonverbal feedback in Zoom.