You can favour other users and mark them with a star. You can invite your favourites to meetings, and you will also receive a notification when one of your favourites has created a meeting or is participating in another meeting.
You can find the list of your own favourites under "Profile" ➞ "My favourites". Here you can also edit your favourites list and remove users from it.
Under "Discover" you can see the users who have favoured you (however, this function is part of Premium).