All computers have an Internet Protocol address, or IP address. It's how they identify themselves on a network.
You have one, and may need to find it from time to time. But knowing an IP address can really come in handy when you're trying to track down people online, like someone sending you phishing emails.
This is useful if you are being harassed by an anonymous source. For example, IP addresses can often be pulled from email messages. But how do you go about matching the IP address with a person?
There are a few sites you can use. InfoSniper is a good one.
Simply enter an IP address. The site will show you its approximate geographic location. (You can also input a website name; find its IP address, then input that.)
You will see information about the owner of the IP address; who they are, and where they're located. You can also link to the WhoIs database. This will tell you who has registered the server or website.