Translation of cookies

Question

My dictionary gives 3 translations for cookie : biscuit, petite gâteau,  and gâteau.   I chose to use petit gâteau, which was marked incorrect.  Since I can't see the cookie and don't really understand if there is a difference, perhaps according to shape or size, could someone elaborate on the nuances?  I have gotten into trouble with this with my friend, who is a native French person, when I used biscuit for cookies that she prepared. Apparently,  there is some disfunction unknown to me.

Accepted Answer

Bonjour Frank,
The translation of the word cookie can be a bit tricky, I agree.
Generally speaking, "a cookie" can be translated with "un biscuit (sec)" or "un gâteau (sec)". If you are making chocolate chip cookies, then, you will use "un/des cookie(s)".
Tout ça me met l'eau à la bouche ! ;-)
I hope this is helpful.
Bonne journée !