between a flan and a quiche? In my opinion a flan is that sponge, jelly, mandarin type thing your granny makes and a quiche is a egg, cheese, plus additional ingredients on pastry. I have heard some people refer to, what I would call a quiche, a flan.
A quiche is strictly an egg and cream/milk based savoury product (often containing cheese though this is not an essential ingredient) in a pastry case.
"Flan" is a wider term that can be applied to either a sweet or savoury product encased in not only pastry but also sponge for instance.