Why is it needed, than it differs from the usual ad with clicks on the site, what advantages does it give? Several times I read in the postal respected people wrote that they use them, but to my shame I do not understand what it is))
This is currently in flux so may change soon. (For example, FB changed the image-type dark post for some users very recently.)
Currently, they sometimes give some format advantages over the main ad format - bigger images, etc.
A post also can be used on multiple ads, but shares all likes and comments made over any of those ads. That's useful for social proof.
How to create it? I can not find