Outlook.com is basically a complete rework of what you currently know as Hotmail but with a clean new user interface. This new user interface is in the Metro style which is also featured in Windows 8, Windows Phone and (to some extend) in Office 2013. To put it bluntly; Its design is a mix of the Windows 8 Mail app, Outlook 2013 and Outlook Web App that ships with Exchange 2013.
Aside from the new interface, there are also a ton of new options, especially when it comes to contact management and interaction. Instead of creating your contacts manually, you can directly integrate your contact lists from Facebook, Google, LinkedIn and Twitter. Skype integration will follow soon (and won’t even require you to install the Skype client)!
To get started, simply visit Outlook.com and sign in with your Microsoft Account. If you already have a Hotmail account, you can sign in with that address too and your account will get automatically converted. You’ll of course then keep your original @hotmail address but also have the option to add a new @outlook.com alias.
There is lots more to this so make sure you read the introduction post at the Outlook Blog. It also hold instructions on how to convert your current account fully to Outlook.com.