|On the Right Side of the Screen you will find the Missions Bar. It can display 1 Main Mission, 1 Dungeon Mission, 1 Action/Sabotage Mission, 1 Ivestigative Mission and 3 Side Missions. However: only one mission can be active at a time and displayed on top. In this case "The Body" is displayed twice because because the Mission tab is unlocked. If the Mission tab is locked you will see missions only once. But you can see that "The Body" is the active mission, displayed above the Main Mission "Dawning of an Endless Night" and you can see that it is a side mission, showing up in one of three slots reserved for side missions.
You can have more Missions than displayed here. If you pick up a new mission and already have one of that type the game will ask you if you want to pause the one already displayed.
You can have a look on the Missions Window to activate and pause missions and to see what missions you have already completed.
During the first Missions you get a Mobile Phone from your faction. Once you complete a Mission a window will pop up, asking you if you want to send a Mission Report. If you do not send it immediately the window will go away and the green Button above the Mission Bar will show up. You will get XP, Anima Shards and Rewards (which mysteriously appear in your inventory) for Missions after you send the Mission Report.