Here's a scary page:
https://www.facebook.com/ads/preferences/?entry_product=ad_settings_screen
Open up the Advertisers section and check out that first section: advertisers who use a contact list added to Facebook. Unlike the other tabs in this section, these ads have nothing to do with your behavior on Facebook or elsewhere on the Internet. All these advertisers got your name the old-fashioned way: by trading something of value for a list containing your contact information.
Per Facebook's vague-but-cheerful explainer, this is "typically" your e-mail address or phone number, but there's really no way to know for sure.
