How do services like Google Maps know what address, city, country, etc. I'm in from my GPS location?

Naively, I would guess that Google has a set of points on a map, and Google just picks the point closest to where I am and assumes that's where I am.

For example, Google might have a set of points representing street addresses. If Google sees that the closest point to me is at 123 Main Street, Raleigh, North Carolina, United States, then it just guesses that my current address is 123 Main Street, Raleigh, North Carolina, United States.