1. Activision will fund the project and Bungie will develop it. The rights to the game belongs to Bungie. Activision has the right to publish the game for the next 8 years. 2. Activision will market it by funding ads and promoting it to the general public. However, much of the marketing design will be done by Bungie since they have a mighty marketing staff. The relationship here is similar to the one they had with Microsoft though Bungie seems to have the final approval on how their game should perceive to the rest of the world. 3. Activision has tons of money and they want to make tons of money. They are also (apparently) the best publisher to support the ambitious project that Bungie's next game is.

They are giving bungie millions to help develop, bungie gets all rights to destiny and Activision gets all rights to publish for 10 years

I don't know the super details of it, but I believe that Activision is literally just publishing the games that they make over the course of ten years. I think Bungie has full creative control, and that we don't need to worry about any influence from Activision. Like I said, I don't know the details, but that's what I think. (From that conference call, it also seems like that Activision is going to be marketing the game.)