How, exactly does HTML5's GeoLocation work?

Question

I know the browser shares my IP address and details of nearby wireless networks to determine my location, but what sort of info does it know about nearby wifi networks?

Answer 1

Data is gathered by Skyhook Wireless (Wikipedia), and they make no distinction between public and private wifi points - they log the locations of all of them. I wouldn't be surprised if the Google Street View vans also logged location data for access points.