https://www.cnet.com/news/facebook-finally-explains-how-it-organizes-your-news-feed/

Though it was announced a day prior to April 1, the new feature is not an April Fool's Joke, a Facebook spokesperson told CNET. It'll begin rolling out this week and be available to all Facebook users by mid-May, according to the spokesperson.

The function will show you what data led to a post being prioritized on your feed. How often you like a person's posts and how often you engage with different mediums like video, photo or text are some examples of information that contributes to a post's prominence.