When the user clicks on a story, Facebook has pop up a link that pops up about sharing maps and publishers. In most cases, this seems to be a very modest attempt to solve the "fake news" problem by telling people whether or not to read from a reliable source (eg AP).
Facebook believes that this feature may be able to let people from unreliable sources to read the information. The company gives an example of a UFO story - to make sure it's a fake news - clicking on the "i" button will pop up a card saying "no information on this site", indicating that it might be unreliable. There is also a warning icon with an exclamation point.
The button is now just a test, so it will not show to all users. Facebook also said "it's just the beginning of the test," which seems to mean that it plans to expand the type of information that the button will pop up.