After you’ve created a Note, Use the share button at the top right corner of the Note to bring up the share widget pop-up. The note can be shared with a contact by simply entering their email id. The share widget will prompt you to invite the person with whom you have shared the note to your workspace.
Sharing without an invitation to your workspace allows the invitee to view the note. If you send an invite, then on joining your workspace, the invitee can comment on the note shared and create notes in the workspace.