In case you couldn't tell from the video, the storyline revolves around Iron Man and Captain America at odds with each other over a few things, namely the idea of superhero registration.

President Kevin Feige said this about how Captain America: Civil War will work without secret identities:

I don't want to give too much away, but needless to say, the generalities of the act are the same. Something happens, perhaps it's cumulative for things that have happened though all of the movies leading up to this point. It has made the governments of the world say, 'We need to have some oversight of these guys.They need to report to somebody.' So...it falls under that umbrella, rather than, 'You have to take off your mask.' It's not about the secret identity thing, as much as it is about, overall, who reports to who, and who can agree to oversight committee. Because as of now, in Avengers 2, there is no more security council, there is no SHIELD, obviously. Stark is paying for it, Captain America is running it, and things occur that will make governments begin to question."