Mission Parameters
The Hanger value is essentially Mission Type, which normally will be "Family Transport" or "Calamari Cruiser". Set a time limit for the mission if you wish, and below that is the option to force the mission to end once the primary goals are completed.
Briefing Officer and Briefing Emblem control a couple briefing images and mission update messages during flight.
There's some Unknown values that you can play with as well here.
The Global Cargo fields are new, and really the only thing you need to worry about is the text box for the cargo string itself. This lets you use a single cargo definition for several flightgroups, and there's triggers designed around this cargo string as well. The offsets are local to the beginning of the GC definition.
There's also a huge chunk of space which is used for editor notes, it doesn't affect the mission in any way.