I am not sure I understand how it works from a user's perspective? I login (using only an email), receive an email with a 'magic link' and this directs me to my authenticated account?

If that is so for the user, how does it work for the site owner? Cierge calls my site and requests a login from a given email, then the site backend conjures a URL which Cierge will use to create the magic link sent back to the user?

It would be very helpful to better understand if they explained the workflow for users and site owners.

If anyone can help me understand this and how it's better than OAUTH (logging FB, Google...) I would be grateful.