Notes that you create will be private when created.  When a note is private, only the creator of the note will be able to view and modify the note.

Making a Note Public 

Clicking on the lock icon on a note inside the notes panel will make your note public. 

Making your note public means that anyone who has access to the Knowledge View will be able to read and modify your note. 

Making a Note Private 

Clicking on the unlock icon on a note inside the notes panel will make your note private.  

You can only see the unlock icon for notes that you own and have made public.