Discuss and learn French: French vocabulary, French grammar, French culture etc.
"Qu'est-ce que..." means "what" when you're asking about what is the object of the verb. (So basically, the thing that has an action done to it-- e.g. the thing that is done, the thing that is eaten etc-- and not the person/thing that is performing the action, doing the eating etc.) So for example:
Qu'est-ce que tu fais? = What are you doing?
Qu'est-ce que tu manges? = What are you eating?
Qu'est-ce que tu as fait ce matin? = What did you do this morning?
Qu'est-ce qu'il préfère? = What does he prefer?
Quel... means "what..." in the sense of "which..." -- in other words, it is asking for specification about which specific type/instance of something, and is therefore followed by a noun indicating which "type of thing" is being asked about:
Quel journal lisez-vous? = What/which newspaper do you read?
Quel ordinateur est le plus performant? = Which computer is most powerful?
Quelles planètes peut-on observer avec ce téléscope? = Which planets can you observe with this telescope?
Notice that "quel" changes form according to the noun in introduces (quelle = feminine, quels = masculine plural, quelles = feminin plural).
In English in these cases, "what" and "which" are more or less synonymous: "which" tends to imply that there is a narrower range of possible choices. French doesn't tend to make this distinction so much, so that quel covers both "what" and "which".
Thank you for clarifying!
I would also like to ask what is the meaning of 'est-ce' and 'est-ce que'?
"est-ce" means "is it...?" For example:
est-ce vrai? = is it true?
"est-ce que" is used to mark a question. For example:
Le ciel est bleu. = The sky is blue.
Est-ce que le ciel est bleu? = Is the sky blue?