People interact through their own connected devices (smartphone, computer, laptop...)
When a session starts, a QRCode and a session code are displayed. The audience can connect at any time using those codes, which remain on screen during the whole presentation.
When you reach a slide that has a question or survey, a countdown shows up, and the audience is prompted to answer with their devices.
When either the countdown is over, or everybody has replied, the results are shown as graphical diagrams.