How to track location via a website?

I just pulled up www.gaiagps.com and the site instantly pinpointed my exact location. How on earth can a website figure out where I am sitting? I think a pop-up asked for permission earlier and I clicked yes, but still—how does the tech actually work?

A computer can track you down via an IP address, sure, but if you want pinpoint accuracy, it needs more specific data—like the info coming straight from your smartphone if your GPS is turned on.
http://en.wikipedia.org/wiki/Global_Positioning_System

If you really want the specifics
http://www.w3schools.com/htmL/html5_geolocation.asp

Scott Perez said:If you want the exact details, check this out:
http://www.w3schools.com/htmL/html5_geolocation.asp

That’s what I was getting at! But before I dive into a massive wall of text, can someone who actually knows just give me the quick version? How does a website actually pin down my location—who's feeding them the data? Is it my ISP, or am I providing it somehow? An IP address doesn't seem accurate enough. Is it because of the Wi-Fi? I'm on a laptop without GPS, and I assume triangulation isn't an option here, unless it's via wireless signals? What if I were using an old-school Ethernet cable? It's incredibly precise for me right now; they placed me within two or three meters, though I imagine if I were out in the middle of nowhere, it wouldn't be nearly as spot-on.