diheadral is the angle in the center of the main wing on your plane. If you look at most planes the main wing will be in a slight "V" shape. The dihedral in an airplane wing will sort of act as a "self righter" kind of like the bottom of a boat hull. If you put the airplane in a turn, the dihedral will help you come back out of it. If you take out the dihedral like in "sport" type planes with straight wings, it generally makes the plane more sensitive on the controls and allows the plane to roll faster.