Missions are one way to earn experience(XP), cash and in some cases special items that will you complete other missions. Missions can be done in various territories located in cities around the world. All mission have requirements in terms of Stamina, Mob Size, Equipment and Level.  You can do the same mission multiple times to master it. Each time you do the mission, its completion percentage will go up and at 100% you will master the mission to gain extra rewards. The number of actions required to reach mastery may be different for each missions based on their difficulty level. Completing the mastery of all the missions in the city will unlock the next mastery level of the missions and you can master then all for even bigger rewards. Each mission has a total of 4 mastery levels.  Missions can be done in various territories located in cities around the world. Additional cities, turfs territories and missions are unlocked as you reach specific levels.