Poesis comes from a Greek word meaning "making" or "creating." In poetry, it points to the act of creating a poem, and sometimes to artistic creation more broadly. The term is related to poetry, but it is not the same word; in literary discussion it usually emphasizes making, shaping, and giving form to language.
Example
The poet treats memory as poesis:
rough notes become lines,
lines become a voice,
and the voice becomes a world.