This is the 8939th most frequent French word.
celles
"Celles" means "those" (feminine plural).
In this sentence, 'celles' functions as a demonstrative pronoun referring to feminine plural nouns that are favorites.
Celles que tu vois sont mes préférées.
The ones you see are my favorites.
Here, 'celles' is used as a demonstrative pronoun specifying a subset of feminine plural nouns (flowers) based on color.
Parmi toutes les fleurs, celles qui sont rouges attirent le plus l'attention.
Among all the flowers, the ones that are red attract the most attention.
'Celles' in this context indicates feminine plural nouns (unspecified objects of preference) being selected based on liking.