Your IP address as other internet users (and web traffic analysis servers) see it is:
Why do I need to know my IP address?
The main reason you would want to know your own IP address is in performing Web Traffic Analysis. You can increase the accuracy of your reporting if you filter out your own views of the site. Most analytics packages allow you to filter out your own visits by IP address.
Can my IP address change?
A large number of ISPs use dynamic IP addresses which change over time. Sometimes these addresses change every time you connect to the Internet, whereas with other providers, they only change occasionally. The easiest way to find out if you have a dynamic IP address is to make a note of your IP address today and come back a couple of times later in the week to see if the address changes. If it changed you have a dynamic IP address.