As JWale indicates, your IP address is where data is sent to, for you to be able to use it. For example, the Answerbank's server needed to know where to send the page you're viewing now.
Assuming that you're at home, and connected to the internet via a router, it's actually your router which is allocated an IP address. You could have a dozen different computers around your house, all connected to that router, and they'd all be using the same IP address on the internet. But if you use a friend's computer, or a public wi-fi connection, any website you use (such as Facebook) will see you at a different IP address.
Most internet service providers allocate IP addresses 'dynamically'. That means that if you disconnect your router from the internet, and then reconnect it, you'll be given a new IP address.
Chris