When you're creating a manual Facebook post, you may find that the fields show up a little bit differently. This is because there are fields within the New Post option that are specific to Facebook. If these fields aren't filled out, Facebook will not get the content that is listed in the non-Facebook fields.
This also means that you can customize the text specifically for Facebook!
The Facebook fields appear with a Facebook icon and will ask you to "Say something about this on Facebook".
Any shared links inserted in the New Post window will also appear on Facebook.