The term distinguishes between sentences where the semantic agent is the syntactic subject, and those where it is the object.
For example: "Bob threw a ball at Suzie" (active, Bob is the syntactic subject) vs. "A ball was thrown at Suzie by Bob" (passive, Bob is the object of a preposition and "a ball" is the subject).
The Wikipedia definition of English passive voice is more instructive: https://en.wikipedia.org/wiki/English_passive_voice .
The term distinguishes between sentences where the semantic agent is the syntactic subject, and those where it is the object.
For example: "Bob threw a ball at Suzie" (active, Bob is the syntactic subject) vs. "A ball was thrown at Suzie by Bob" (passive, Bob is the object of a preposition and "a ball" is the subject).