Umm... Not a lot? The bond between a player and an AI? What happens if you give humanity access to incredible abilities? Some use it for good, some for evil, others for personal gain? That's about it, Titanfall really doesn't shoot for the stars with its world. The campaign was fun but it really only existed to set up the multiplayer, there isn't really any lore about time traveling aliens or and all consuming darkness like Destiny has. Titanfall is about a soldier living up to his successors glory, while Destiny is about a chosen one saving what remains of humanity