The feature works exactly the same, but should be clearer for users
Facebook survived for this long and thrived when competitors faltered because it knew when to borrow a good idea, shamelessly or not. And it's not stopping now, the site will take any feature they like on other sites and make it their own.The latest example of this is renaming the "Subscribe" button into "Follow."
This doesn't really require any sort of explanation. "Follow" is a more accurate description of what the button does and it's already engrained in the collective consciousness from Twitter.
Facebook used "subscribe" in an attempt to stand out perhaps, but it seems that it realized it was just confusing its users and denying people a bigger audience.
The new button is being rolled out to everyone that has enabled the "Subscribe" feature for their profile.
As the names, both of them, suggest, the button enables Facebook users to follow people they find interesting without friending them, something that was impossible until a year ago.