Notes: Keep Sensitive Data Private with Private Notes

Your reps rely on notes to streamline their workflow and increase productivity. With private notes, they can record sensitive information while keeping the note in context. Reps can also selectively share private notes. This change applies to Lightning Experience and all versions of the Salesforce app.
Available in: Group, Professional, Enterprise, Performance, and Unlimited Editions

As your reps develop business relationships with their customers, they can become privy to confidential information. They could learn about an upcoming product launch, or the timing of a new initiative. They want to record this information, but don’t want everyone to be able to see it. That’s when private notes come in handy.

Your reps have these sharing options for private notes.
Visible to Records
Anyone with read access to the related record can see the note.
Privately Shared
The note is visible only to the rep and people the rep has explicitly shared it with.
Only the owner of the note can see it.