What does "knowing" mean in the definition of metaphysics?

Context:

metaphysics
n.
the philosophical study of being and knowing.

Wiki:
Metaphysics is a traditional branch of philosophy concerned with explaining the fundamental nature of being and the world that encompasses it.,[1] although the term is not easily defined.[2] Traditionally, metaphysics attempts to answer two basic questions in the broadest possible terms:[3]

1.What is ultimately there?
2.What is it like?

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Here is a definition for the word knowing:

a clear and certain mental apprehension.

But it seems not very suitable for metaphysics.