This is the 2638th most frequent French word.
quel
"Quel" means "which" or "what" in English.
Here 'quel' is used as an interrogative adjective modifying 'livre' (book) to ask about a specific choice among books.
Quel livre étudies-tu aujourd'hui?
Which book are you studying today?
In this sentence, 'quel' is used as an interrogative adjective modifying 'chemin' (path) within an indirect question to express curiosity about a choice.
Je me demande quel chemin il prendra demain.
I wonder which path he will take tomorrow.
Here 'quel' is again an interrogative adjective modifying 'genre' (kind) inquiring about a preference regarding movies.