Depending on the type of training event you're attending, communication may be a big part of it.
A training event's instructor may expose two communication methods:
Private/Public Textual Chat
Audio and Video
Assuming both video and chat are enabled, the communication panel (on the right) will look something like this:
You can mute the stream by using the controls located on the stream itself, in the top right part of the screen, hovering the screen will give you a better look at them.
Asking to Speak
If the instructor enabled hand-raising, you will be able to ask to be heard and seen by the rest of the class by clicking the "Ask to Speak" button on the lower part of the video section.
If the instructor decides to accept your request, you will be prompted to accept their invitation to speak:
Once you accept, you will have the ability to broadcast to the classroom, alongside the presenter:
The bottom part of the panel allows you to use the public/private chat. The upper part of the chat client will indicate the current chat.
By default, public chat is selected, and anything you write there can be seen by all other students and instructors.
If you wish to conduct a private chat, simply click the context button (Hamburger icon on the top right part of the chat area) and you will be presented with a list of instructors and students to choose from.
After choosing someone, writing anything in the chat panel will send a private message to them. In turn, they will see a notification dot appearing on the context button. Once clicked, they will be able to respond.