what do the stars (***) behind a mission type mean?  ???

There are 4 ways to end a mission. Land, crash land, bail out and go for debriefing instantly.
Does it make a diference to actually land your aircraft instead of jumping to debriefing once finishing all your goals? In CFS 1 it made a diference, that's why I'm asking...  ???

Yes, it doesn't matter if you land, crash land or bail out or go for debriefing once you've completed all your goals in order to complete the mission. Still there might be a diference in the Prestige Points awarded. Or else.. why would we try to land without our landing gear and risk death when we could just end the mission...
I know for shure that in CFS1 it was impossible to win the top medals without landing the aircraft yourself.

And about the ***, yes I also think that.. Still , in 'Help' they say nothing afects more the enemy than bombing factories. But factory bombing are rarely *** missions, normaly it's a * mission. My theory was that the *** meant the short term impact on the war theather. When there is a ground invasion ocurring you get dozens of *** missions in the invasion sector, all about bombing tanks, bunkers, ammo depots etc..