A quiche is a type of flan...which is a pastry case with a custard style filling. The word flan used to mean 'flat cake'...
Quiche is a term for an open pie...which has a custard style filling. And the word derives from French region of Lorrain, hence quiche lorraine is one of the best known versions...
But in Spain a flan is a custard pudding - no pastry....
In British English usage, flan may be various kinds of tart or cake with a sweet or savoury filling, often custard-based.
In the US, and in Spanish, flan is a cr�me caramel.
An egg-based savoury dish closely related to quiche.
Quiche is pastry - baked blind with eggy (and other stuff) filling, i.e. savoury. Flan is sponge with fruit and jelly type stuff. i.e. sweet. And remember - real men don't each quiche!