When you mention a person in a comment, they’ll be notified. This both alerts them to your message and encourages them to take part in the discussion. It’s a great way to call-out to people who may have a valuable contribution to make to a shared document. It’s also very useful for reminding people (particularly students and colleagues!) that they need to contribute, or for directing questions to specific individuals.
It’s super easy to mention someone in a comment.
Within the comment box, type + or @ followed by the person’s name or email address. If the file is not already shared with that person, you’ll be prompted to adjust the sharing permissions.
Note: Mentioning a person in a comment does not make that comment private. All comments in a shared document are visible to all collaborators.