Microsoft's Major Nelson has provided a walkthrough of the Xbox One's Friends App.
A big feature shown in more detail is the ability to follow people you're not friends with, such as celebrities or people who regularly upload cool gameplay clips. If that person follows you back, you will then appear on each other's friends' list.
Nelson also demonstrates the feed, which highlights what your friends are doing in real-time, whether that's playing a game or uploading a gameplay clip; the new look for profiles; the multiple ways in which you can filter and arrange your list of friends; 'favourites', which allows you to keep tabs on a core group of friends, or as Nelson puts it "a snapshot of those you care most about on Xbox LIVE".
You can also 'snap' the activity feed to the left-hand side of the screen, giving you a constantly updating window into what your friends and the people you follow are up.
Xbox One launches on November 22nd, 2013.