The Harry Potter movies are just like the books—their titles follow a pretty simple formula. Each one is named Harry Potter and the Something Weird and Mysterious You Won't Understand Until You Actually See the Movie.
This one is no different.
Harry Potter and the Order of the Phoenix is about—you guessed it—our favorite boy wizard finding all about the Order of the Phoenix. Apparently this is a super secret group that Dumbledore founded back when Voldemort came into power. It would have been the 1970's according to the timeline in the book and based on the costumes in the picture Sirius gives Harry at King's Cross station. Groovy.
It's pretty cool because Harry's not only getting more info about his parents—who were charter members of the group—but he's finding out more about how the older generation fought out Voldemort. After all, if you don't understand where you came from, how can you know where you're going?
Harry definitely needs some direction right now because he's dealing with way more than any fifteen-year-old kid should have to.