What features does Xbox Live Subscription provide?

Ok, I have a Xbox One. I understand of needing a Xbox Live to connect to the internet to use various apps, but is Xbox Live separate from Xbox Music? Will I need to buy another separate subscription for Xbox Music? And does Xbox Live Subscription fall under having a Skype premium subscription as in it gets you the ability to use premium features of Skype. I was hoping to get some clarification on what features Xbox Live Subscription gives. Thanks!