Facebook is a type of discussion forum, that tries to organize discussion content in an intelligent newsfeed based on multiple factors, including your relationships, your interests, and your historic engagement activity.
From a content provider perspective, it gives publishers easy platform to share their content and attempt to promote it, using socialization features, to maximize its impact on potential consumers new streams, and get as much engagement as possible.
It is also a video streaming platform, where you can literally just sit back and watch it like a TV. In this way, it separates the video from its original post which encapsulated it.
When news is posted to the platform, it can trend significantly, and give us the news publisher much wider exposure to the story than could be possible if only published two windows publishers paid subscribers. The downside is, that the majority of people only consume the headlines, and many times the contents of the story get rehashed in the comments section, negating the need for having a paid subscription to consume the news. The jury is still out on whether Facebook helps news publishers, hurts them, but starting with Australia, several governments around the world have taken issue with Facebook profiting on advertising around stories that they didn't pay for.
In theory, it is a good platform for sharing interesting web content, but in practice, if you share a link to a tweet that is going viral, the presentation of said link, and the news stream algorithm will not give it nearly the same exposure, compared with taking a screenshot of the tweet and posting it directly to Facebook.
Similarly, if you share a link to an interesting YouTube video, or screen capture the video and post it as a new video to Facebook, the latter will get priority in the news streams. This practice is known as #freebooting, See @kurzgesagt's video to learn more.