Conversation so far:
What did Aesop do as a fabulist?
Aesop was a Greek fabulist and storyteller credited with a number of fables now collectively known as Aesop's Fables.
What other works did Aesop write?
Does anyone have the book Aesop's Fables?
Although his existence remains unclear and no writings by him survive
Why is Aesop most famous for?
Aesop is credited with a number of fables now collectively known as Aesop's Fables

Question: What did his fables talk about?
Self-contained rewrite: What did Aesop's fables talk about?