Captain Marvel is set in the 1990s, setting it before most of the events in the Marvel Cinematic Universe that we’ve seen thus far.
This gives us an opportunity to see Samuel J. Jackson as Nick Fury in a world before he is aware that superheroes exist, and it also gives an opportunity to see a character like Agent Coulson return to the film side of the MCU.
However, the movie will also deal with the Kree as the villains, the same characters we met in the first Guardians of the Galaxy movie, meaning that it opens up the opportunity to do more with characters like Ronan the Accuser and Korath the Pursuer, (and possibly other characters whose middle name is “the”).