Sunset Overdrive has three kinds of mission-like single-player events to engage in. Missions are the “golden path” of the campaign, the tasks necessary to advance the plot and progress in the game. Quests are optional side tasks, which are usually favors for the eccentric cast of characters with whom you’re stranded in Sunset City. Finally, Challenges are instanced, arcade-like tasks.
Sunset Overdrive Official Strategy Guide Missions