What is a conference number? How can I use this number?

A conference number is a unique number which you can create and share with your participants while launching the session and sharing the meeting room URL link with your contacts. You can even use when you are connected to an audio conversation like a phone conference bridge or Skype. 

It’s accessible when the chat session appears onscreen and you see Conference text field where you can give number to the session and click Ok. Only the presenter can edit the conference number.