The Rebel Alliance wins a major victory thanks to Luke, Leia, Han, and *wait for it* Darth Vader. In an epic final battle, Palpatine shoots deadly thunderbolts of lighting out of his hands at Luke (as one does), causing Vader to jump in front of him and protect his son. Then, Vader casually tosses Palpatine's body into a pit located conveniently in the same room, getting rid of the Emperor once and for all. Vader quickly succumbs to his wounds, and while the Empire is splintered following his and Palpatine's death, it's still very present in the story and will most likely be continued in episode seven with the introduction of villain Kylo-Ren.
(Side note: the main characters celebrate the big W by partying it up in the woods afterwards with a bunch of small, living teddy bears called Ewoks. So, there's that.)
