In Fellow, there are several different types of note series with different visibility.
You'll be able to tell the type of note series (and the related visibility) by looking at the icons by the meeting name. This is the general structure:
Types of note series
Meetings: Only visible to meeting attendees
1-on-1s: These are only visible to the two people involved
Private: Visible only to you
Shared: Visible to whoever it has been shared with
Public Links: Visible to anyone with a link
See who has access to the note series
By clicking on the blue Share button, you can see the names of the people who have access to the notes.
You can also click on the avatars in the note to see who is shared on each note!
But for public links, you won't be able to identify who is watching the note. Instead, these people will appear as Anonymous.