This allows people to communicate while others are speaking, without the need to interrupt the speaker (eg: non-violent communication)
Sign gestures are used to facilitate meetings in a decentralized fashion.
Here is a list of useful signs, feel free to adapt depending on the context.
Sparkly fingers: I love what you are saying, i couldn't agree more.
Raising one hand: I would like to ask a question or add something to what you are saying.
Rolling hands: This explanation is getting too long, please get to the point.
Hat hands (A.k.a. STFU):I've heard enough from this speaker, i would like to hear someone else's opinion or change topic.
Two hands up (A.k.a. "pop the stack") let's get back to what we were discussing before.
Two hands pointing at a person (a.k.a. pass the mic): I would like to hear this specific person. This can be done either by the person currently speaking, or by other participants in case they feel the pointed person is not being heard.