This sentence means "(this is) what you know"

The usage of "suo" here is called suo structure, which refers to the object of action, similar to the English object clause. What you know is what you know and what you know.

Why not use "you" as the predicate? This is an inverted sentence, in which "Zhi" is the sign of the preposition of the object "What bothers you" and "What bothers you" is "What satisfies you?"