Only organizer/initiator shares his screen.
Screen is one-way; however audio is two-way.
Organizer can speak with all users.
All users can NOT only view organizer's screen; but also they can talk with him.
Users can NOT hear/talk each other. It is one-to-many kind of topology; it is NOT mesh or many-to-many.
(Install Chrome / or / Firefox extension) - Extensions are open-sourced!