Did you just notice that your Hotmail account looks completely different today? It means that Microsoft has just upgraded you to the next generation of webmail, successor to MSN / Windows Live / Hotmail. You can keep your existing Hotmail address, or sign up for an outlook.com email address. If you stick with your current account, you can "downgrade" your experience and switch back to the classic Hotmail interface in a couple of clicks. There is no telling, however, on the duration Microsoft will allow users to retain the traditional Hotmail look and feel; at some point, it will probably "force upgrade" everyone to the new Outlook.com.
First, sign in to Hotmail account using your normal credentials (full email address ending in "@msn.com", "@hotmail.com", or "@live.com" - or a localized version of these domains for your country). Once logged in, go to your inbox and proceed as follows:
Conversely, you can switch from Hotmail to the new version at any point - here's how:
Should you decide at any point to try out the new Outlook.com, click on the "Options" menu, and pick "Upgrade to Outlook.com". A popup will open, outlining the compelling features a click away, and include a short video; click "Maybe later" to stay with Hotmail, or click "Upgrade to Outlook" to switch to the new version of Microsoft's webmail service.
Caution: beyond the initial launch phase, which lets you switch back and forth between Windows Live Hotmail and Outlook.com, it is likely that at one point you will no longer be able to retrograde back to Hotmail, even if some users are still able to use it. For smooth transitions on a massive user base like Hotmail's, it is common to do it in batches, to contain any problem to a targeted segment.