"You are a cook."
Translation:Tu sei un cuoco.
You are mostly right!
è would be "he is" or "she is", sei would be "you are".
In your example sentence you used the wrong gender for the cook - it would be "lui è un cuoco" (he is a cook) or "lei è una cuoca" (she is a cook). In English we don't have different wording for male and female cooks, but think of it along the same lines as "actor" and "actress". You would want to say "he is an actor", not "he is an actress".
The verbs "essere" and "stare" can both mean "to be" but "stare" is not correct here. "Stare" usually means "to stay", "essere" usually means "to be" or "to exist". For beginners, when in doubt, I'd advise using "essere". Essere is used for identity, nationality, and profession. Cook, of course, is a profession. italiantranslation-teaching.com/learn-Italian/Italian-grammar-difference-between-essere-and-stare/
In spanish you can say "Eres cocinero". Which means also you are a cook, so i marked Sei cuoco. is this wrong? Can you use that expression in italian? in spanish you can use it like that but most of the times you can algo use it as a question "Are you a cook?" In spanish without the article refers more to a general sort of profesion. just asking to see if its sort of the same in italian.
Yeah….I don't think you need the article either. http://forum.wordreference.com/showthread.php?t=493433
If you're talking about a woman then saying "tu sei una cuoca" would be right (not sure if duolingo would mark this as right though - be warned) but "una cuoco" isn't right because the article una is feminine and cuoco is masculine. Cuoca is the feminine and female version of a cook.