How do you 'check-in' somewhere on Facebook?

How does facebook know where my HOME computer is?

• Normally my isp comes up in a nearby City, but I was messing around to see if I could do a "checkin" on facebook from my home computer with touch.facebook.com. , and it listed all the places near me. How did it know my nearest buisnesses, stores etc!?

• Answer:

  You have two IP addresses. The Dynamic IP address which is the one most people are familiar with, and as you said, isn't even close to your actual location. It can be changed by you at any time. Can be changed by the provider at any time. Or a group of customers could be issued the identical Dynamic IP address by the ISP. It's possible that they have the right to get your Static IP address from your ISP. The Static IP address is issued by the ISP and never changes. It's required by the Federal Government as a means to track any illegal activity a computer is used for. Your ISP is required to maintain records of web sites your computer is linked to for a specified time. Some people say this is 6 months and some say it's a year or longer. Any illegal web site activity can be linked to a specific computer at a specific address in the US. Since the government uses facebook to watch certain individuals, I would assume that facebook has a member's Static IP address for security reasons. I have tried the same thing and my Dynamic IP address is 15 miles from my actual location.