Facebook extends the algorithm changes and surveys to predict and prioritize Facebook Pages and Groups that you care about the most.
Recently, Facebook updated their algorithm with two major changes prioritizing which friends you might want to hear from and links you might consider the most worthwhile. This update adds Facebook Pages & groups to it.
These changes are further being widened with Pages and Groups. Facebook continued to survey and has updated the algorithm by using the survey results.
Few of the indicators of how much you care about a Group or a Page is how long you've followed it or been a part of and how often do you engage with the Page or the Group.
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Similar to the last update, the changes don't mean that you'd only see posts from Pages and Groups, it means that you'd see posts from these Pages and Groups higher up in the feed.
In context to the last algorithm update, Facebook mentioned that they would be updating their prediction models on a timely basis. Although it's unclear if we can expect the same with these updates.
The motive of Facebook making these updates is because they believe friends are not the only reason people come to Facebook and a prioritized feed would provide a better experience.