This is the 14742nd most frequent Russian word.
писателя
"Писателя" means "writer" or "author" in English.
In this sentence, 'писателя' is used to indicate possession, referring to the writer's ideas, and is in the genitive case.
У писателя было много интересных идей.
The writer had many interesting ideas.
Here, 'писателя' is in the accusative case, showing that the writer is the direct object of the verb 'встретил' (met).
Я встретил известного писателя на конференции.
I met a famous writer at the conference.
In this context, 'писателя' is in the genitive case, used after the preposition 'о' to indicate the topic of discussion.