Ubisoft recently began showcasing its co-op in Splinter Cell Blacklist, and today the company delved into a bit more detail. The 14 unique co-op missions are split into four mission types, each given by a different member of the team.
A post on the PlayStation Blog details the first two. Isaac Briggs missions are most similar to a co-op campaign, but they're unique stories that fit into the rest of the game. The Grim missions from Anna Grimsdottir, meanwhile, focus more on stealth and not leaving behind any trace of your presence. That probably means no kills, and no sightings.
The blog didn't detail the other two mission types, but we know combat has been split into three play-styles: Ghost (stealth), Assault (shooting), and Panther (mix). The Briggs missions can be approached any of the three ways, and the Grim missions are Ghost-focused, so it would make sense for the two remaining to be Assault and Panther.