When you link your Skype and Microsoft accounts, your Microsoft contacts appear in your Skype contact list and your Skype contacts are displayed within your Microsoft contacts. If you have a friend in Skype and in Messenger, that friend will appear twice within Skype.
When you’re signed in to Skype with your Microsoft account, you can call, instant message and send SMS messages to your Messenger buddies, even if they’re not on Skype.
Linking your Skype and Microsoft accounts does not link your billing information. Only your email address and contacts are shared between your Skype and Microsoft accounts. Billing-related details – like billing address and credit card information – are used only in the account you entered them in.
There’s no change after your accounts are linked. Any products you purchased before you linked your accounts are managed the same as before. You’ll manage your Skype products – like Skype Credit and subscriptions – in your Skype account, even if you sign in to it with a Microsoft account. And you’ll manage your Microsoft products – like Xbox Live subscriptions – in your Microsoft account.
Skype will automatically use your Microsoft account primary email address when your accounts are linked. So if you change the primary email in your Microsoft account, you will sign in to Skype with that new email address. Likewise, if you change your Microsoft account password, you will use the new password when you sign in to Skype with your Microsoft account.
Apart from your contacts, email address and password, no other information is shared between your Skype and Microsoft accounts.
Find out how to link your accounts.