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How did Ludwig Wittgenstein distinguish certainty from knowledge?

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Four colored straws in a glass of water appear bent at the water's surface, visually demonstrating the refraction of light. — Epistemology The refraction (bending) of light as it passes from air into water causes an optical illusion: straws in the glass of water appear broken or bent at the water's surface.

In his work On Certainty, Ludwig Wittgenstein argued that knowledge and certainty are fundamentally distinct categories rather than different degrees of the same mental state.12

He rejected the traditional view that equates certainty with a form of apprehension, "seeing," or internal consciousness. Instead, Wittgenstein distinguished them as follows:1

Knowledge: Often associated with the capacity to provide grounds or justifications within specific contexts.1
Certainty: Wittgenstein identified certainty with "acting" rather than a mental state. For him, a proposition is certain when its truth is presupposed by the social activities—or "language games"—of a community.1

Ultimately, Wittgenstein maintained that neither concept entails the other; it is possible to possess knowledge without being certain, and to be certain without having knowledge. He famously noted that while the process of justifying evidence must eventually come to an end, that end is not found in propositions that strike us as immediately true, but rather in the shared human actions that form the foundation of our language.1