The Injustice universe is set in an alternate reality where Batman and Superman take opposing sides after a fallout following the death of Lois Lane at the hands of Batman's arch-nemesis, the Joker.
Well, technically, Supes killed his wife. Joker gassed him with Scarecrow's fear toxic, leading him to think that he was fighting against his biggest fear, which happens to be Doomsday.
In any case, this sets off a cascade of events that occurs through many years and has so far spanned two games, multiple comic books that detail the events before, in between, and after the Injustice games, as well as an upcoming animated movie adaptation.
With the Injustice animated movie set to premiere sometime this fall, a preview or trailer was expected to drop soon.
However, while an Injustice animated movie preview did drop, it's not exactly from official sources.