The main communication tool on the webinar is a chat where the participants can answer the presenter's questions and talk to each other.

Participants can use the general chat or send personal messages. To start chatting, type the message and click the Send button or Enter on the keyboard. 

To ask the presenter a question, use the Questions tab. There, the presenter won't lose the question and will reply to it. 

Also, the presenter can communicate to the participants via the microphone.

Make sure that users' microphones are enabled. The crossed out microphone icon next to the participant means that the mic is blocked. Click it to enable the microphone.