Facebook pages have gone through many changes over the years, the most recent change being the new design. One thing that's been pretty consistent since the beginning is EdgeRank, an algorithm that determines how content is displayed on people's newsfeeds.
One thing that has been known for some time is that if a friend or fan doesn't engage with your posts (liking, commenting, sharing), over time they will see them less and less. A way that marketers have helped alleviate this problem is by asking to "Like" a post.
Unfortunately, this has lead to a new term which I talk about in the video below, as well as some bad examples, and other pages we can learn from.