Here is the explanation I gave (correct me if I am wrong...) :
"Croquants and tuiles are generic terms. The difference stands in the thickness of the preparation.
A croquant is thicker than a tuile (generally > 3mm). Its name means that it has a crunchy texture (croquer = to munch).
A tuile is 1 mm thin and therefore very fragile. It is light and doesn't resist at all in your mouth (and even sometimes on the way to...). It is generally used when plating as a decoration on a dessert (e.g. chocolate tuile) or on a savory dish, like a parmesan tuile on a fish fillet.