If you have an account with a web service like Google, LinkedIn, or Twitter you can add it to your Microsoft account. This allows specific info to be shared between the two accounts. For example, if you connect a Google account, you can choose to see your Google contacts' email addresses in the People and Mail apps. Microsoft won't share info associated with your Microsoft account without your permission.
You can see which accounts you've already connected by going to your Microsoft account profile and looking at the icons in the top right corner.
Add an account to your Microsoft account
Go to your Microsoft account profile and sign in.
Select Add in the top right corner.
Select the account that you want to add, and follow the instructions to sign in and connect.
Manage or remove a connected account
Go to your Microsoft account profile and sign in.
The icons in the top right show the accounts you've already connected. Select the one you want to manage.
Use the check boxes to select the settings you want and then select Save. Or, if you want to remove the account, tap or click Remove this connection completely.