What does it mean when someone has the same ip address as you?

I would say it is "possible", but very, very unlikely. I say this in the context of the addresses of the computers on the internet. Each one MUST have a unique IP address, or it will be confusing as to which one you should be communicating with. Now, it would be possible for someone to set their IP address to be the same as another computer, but the only possible reason would be to try and pretend to be the real "owner" of the IP address for some reason. I would not expect it to be very effecive unless someone really knew what they were doing and how the Internet works. And the truth is that many, many computers with Internet access DO have the same IP address. They are often something like 192.168.xxx.xxx. The reason this is not a problem is that they are behind a router or other device like perhaps a firewall that uses what is known as Network Address Translation or NAT. This is where the rounter has a unique IP address, but then transfers information to local computers that are connected to it that have a privit set of IP addresses. This provides protection from the outside, since no one can know your "real" IP address and connect to your PC, but also allows for many more computers to connect to the web then would be possible just using the numbers available with the standard IP addressing. There is a new scheme of Internet addressing that you may be interested in: google.com/search?&q=IP+v6">http://www.google.com/search?&q=IP+v6 Most internet service providers have more customers than dedicated addresses. When you logon to your service, you are assigned one of their addresses. When you log off, that address becomes available to another user. Some businesses have a central computer which stays connected to the internet and all the computers on the network will have the same IP address.