Why does facebook now think my laptop has a different IP address?

I have logged into facebook as usual from my own laptop this morning. But I have received e-mails saying that I have logged in from a new IP address. It is me logging in, as the times match. But does this mean something has been done to my computer without my knowledge or is it likely to be a fault at Facebook?

What is a VPN?

VPN is (Virtual Private Network) were first used by companies to enable their employees to securely access internal systems such as email remotely (e.g. from home or while on business trips). Today they are increasingly being used for personal use by individuals to protect their privacy while online in public places (e.g. when using the wi-fi connection in a cafe) or in a country where the internet is censored / blocked (e.g. China, Saudi Arabia��).