Reactions
Polls, hand signs & emojis
Polls, reactions, and hand signs give you live data on where the group is, which is something a screen otherwise keeps hidden from you.
In a room, you can read the group: the nodding, the uncertainty on faces, the hands going up. Online, you get a grid of small faces and often not even that if cameras are off. Reactions and polls are the tools that restore some of that signal.
Used well, they make participation continuous rather than episodic. A quick poll mid-session tells you if people are following. A thumbs-up reaction tells you the instruction landed. An emoji in chat tells you the mood. Used badly (overused, made mandatory, or used without reading the results), they feel like busywork.