We use .note for backing up.
Notability by default saves your notes in .note format. When you back up your notes to Google Drive they save as a .note which is basically the raw version. If you need to restore your notes then those raw notes will come back down from Google Drive, as if nothing happened!
Google can save these notes but cannot read them. If you’re in Google Drive attempting to look at a note in the .note format you will get an error “Unsupported Filetype”
We use .pdf to email or export out of Notability.
If you’re sending a note as an email or if you’re dropping back to a Schoology assignment the note will send as .pdf automatically unless you tell it otherwise. Sending a .pdf is ideal so that others can view your work and annotate over your note without altering the original.