This is the 130th most frequent Slovenian word.
katere
"Katere" means "which" (feminine plural form).
Here, 'katere' is used as an interrogative pronoun referring to plural objects ('books').
Katere knjige so tvoje najljubše?
Which books are your favorite?
In this instance, 'katere' functions as a relative pronoun referring to the antecedent ('tiste').
Izberi tiste, katere želiš prebrati.
Choose the ones which you want to read.
Here, 'katere' is used as a relative pronoun connecting the noun ('slike') to the clause providing additional information.