Quel is the French equivalent of "which" or "what" used directly before a noun, and it agrees in gender and number with that noun: quel (masculine singular, quel âge as-tu?), quelle (feminine singular, quelle heure est-il?), quels (masculine plural, quels films aimes-tu?), and quelles (feminine plural, quelles couleurs préfères-tu?).
Quel can also be used with être to ask for identification rather than a choice: quelle est ta couleur préférée? (what is your favorite color?), quel est ton nom? (what is your name?). In this construction quel still agrees with the noun that follows être, not with anything else in the sentence.