What is the difference between the interrogative pronouns "Qué" and "Cuál"?

A common mistake among A Level Spanish students is to mix up the interrogative pronouns "Qué" and "Cuál" when formulating questions in Spanish. The reason for this is that, even "Qué" and "Cuál" can be roughly translated as "What" and "Which" in English, there are some subtle differences in meaning which result into this translation not being possible in every situation.

The interrogative pronoun "Cuál" is usually used to ask for the identity of a person or thing among various possible choices. On the other hand, the interrogative pronoun "Qué" is used to ask for the kind or class to which a certain person or word belongs. Thus, the sentence "¿Cuál te gusta? (Which one do you like?)" asks for the identity (Which one?) of the object you like. On the other hand, the sentence "Qué te gusta? (What do you like?)" asks for the kind of things you like.

It is also common to use the article "Qué" before nouns which an equivalent meaning to the pronoun "Cuál". Hence the sentence "¿Cuál te gusta?" would be equivalent to "¿Qué coche te gusta? (Which car you like?)" if we were talking about cars. However, if we were talking about vehicles in general, the use of the formulation "¿Qué coche [...]?" would include an extra piece of information – while "¿Cuál te gusta?" would be referring to a vehicle (namely a motorbike, a truck, etc.), the construction "¿Qué coche te gusta?" would be referred only to some of those vehicles (those which fall under the definition of car).