This is a unique 9-digit ID number that your meeting participants use to access your meeting via the Meetoo app. Each meeting you or your colleagues set up in your Meetoo dashboard has its own unique meeting ID.
You can see your Meeting ID in the list of meetings in your dashboard:
It is also shown once you click on the meeting name to open the meeting interface:
Your meeting participants enter the meeting ID on the login screen in order to join your meeting: