In order to get the most out of Windows 10 you will need a Microsoft-account. It is free and it provides you with several advantages.
You use your Microsoft-account to log on to your computer. If more users are using the same computer, you can have separate Microsoft-accounts.
The account is also used to access all Microsoft online services – including, OneDrive, Office 365 and outlook.com (formerly hotmail.com). You only have to remember one password. All of these services are built into Windows and once you have logged on to your computer with your Microsoft-account, you are automatically logged in to all services.
Likewise, you will need your Microsoft-account when downloading apps in the Store. You can use a credit card for your account, if you want to buy apps. In addition, the account can be used for purchasing movies, TV-series or Xbox games in other online Microsoft stores.
If you have more than one computer, you can use the same account for all of them. Your settings, such as, background image and colour theme is automatically synchronized on your computers, for a personalized experience.
You will get the opportunity to create a Microsoft-account during setup when starting your new computer or upgrading from an older version of the operating system. If you oppose the recommendations of Microsoft and instead choose a local account, you can later change to a Microsoft-account by opening the start menu and selecting Settings > Accounts > Your Account > Sign in with a Microsoft Account instead.