Your Microsoft Account is essentially your personal key that opens the door to a myriad of Microsoft’s connected services.
When you create a username and login to gain access to any of Microsoft websites, forums or internet marketplaces, such as the Microsoft Community Answers forum or the Windows Marketplace, you have just created a Microsoft account, and that Microsoft account login & password opens up your computer’s and phone’s access to these connected services.
I’m not going to try to describe all the ins and outs of a Microsoft account in this article – that would take a book! No, the best I can hope to do in this article is leave you with a basic understanding of what a Microsoft account is and why you need one to get the most from your Windows Phone. Of course, you can use the phone without setting up a Microsoft Account on it, but to get the best functionality out of your phone you’ll need to set up a Microsoft Account on it to take advantage of all these connected services.