In Fellow, there are several different types of streams with different visibility.
You'll be able to tell the type of stream (and the related visibility) by looking at the icons by the stream name. This is the general structure:
Types of Streams
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 stream
For streams that are visible to more than 1 person (ex. Meetings and Shared), you'll be able to see the number of people who have access to that stream. (Note: this will appear different in 1-on-1 streams)
And by clicking on that number, you can see the names of the people who can edit the stream.
But for public links, you won't be able to identify who is watching the note. Instead these people will appear as Anonymous.