1.

Audio
You can have two types of audio modes.

Listen only - You can hear the teacher, but not the other way.

Microphone - You have to select this to talk to teacher. Please note that a microphone icon will appear to the right bottom screen when this mode is on. You can turn off microphone mode by clicking again

2.

Webcam (optional)
If you are using a webcam you can find this control active. You can turn off webcam by clicking on the icon.

3.

Chat
Assuming you are using a desktop browser, you can find chat panel to the left of the video screen. However, in mobiles you can find this by clicking on the user menu at top left corner.

4.

Whiteboard
The whiteboard is a writable area, normally hidden when the video is full screen.

5.

Notes editor
This is a simple text editor. Note that, while using this in mobiles, you have to activate notes editor using user menu.