If you're following the Avengers vs X-Men event, you probably already have an idea of what is happening, but if you're not here's a brief run down.
Tony Stark and the Avengers noticed that the Phoenix Force (that big evil thing that possessed Jean Grey) was flying through space and headed for earth. They assumed it was coming for Hope Summers (the first mutant born after the House of M story arc) to possess her and destroy the world. Cyclops assumes it's coming to make her a messiah for the mutant race.
SPOILERS for Avengers vs X-Men below.
In the latest issue Tony Stark thought he destroyed the Phoenix force but he actually just broke it into five pieces. From there it fell to earth and has chosen it's host, get your first look at who they are and what they look like below, courtesy of USA Today.
Avengers vs X-Men Issue 6 Exclusive First Look
Yup, the Phoenix force has chosen Cyclops, Namor, Emma Frost, Colossus and his little sister Majik.