This is the 2nd most frequent French word.
le
"The" (definite article, masculine, singular).
Here, 'le' functions as a definite article indicating a specific 'livre' (book) that is being referenced in the conversation.
Je vois le livre que tu lis.
I see the book that you are reading.
In this case, 'le' acts as a definite article to generalize 'chocolat' (chocolate), referring to the substance or concept of chocolate without specifying a particular instance of it.
Il aime le chocolat.
He likes chocolate.
In this sentence, 'le' is a definite article referring to a specific 'chat' (cat) and 'sofa' (sofa), marking them as known entities in the context.