How does facebook suggest friends to people who don't use facebook?

[CSMStudent]

I have a friend who does not have a facebook, but received an email from facebook that stated that (lets call her sue) an old high school friend had just joined and had suggested she join. Now there was also a list of people she might know. In that list was her hairdresser. Now there is absolutely no connection between sue from Minnesota and my friends hairdresser from Colorado. How did facebook know that my friend knew this hairdresser based on an invite from her old high school friend sue?

[Naveeed Nasib]

go friend tab then click on the invite friend there is an option of email just mail your Friend