What is an Increment?
The increment is the sum of all backlog items completed during a sprint plus all prior increments — a concrete, usable, potentially releasable step toward the product goal. "Potentially releasable" is the bar: it meets the definition of done whether or not the PO chooses to ship it.
The decision to release is business; the readiness to release is engineering. Scrum requires the second every sprint and leaves the first to judgment.
Worked example
Sprint 9's increment includes working invoice payments — tested, documented, deployable. The PO holds the release two weeks to align with a marketing launch: a business call. What she never has to ask is "but does it actually work?" — the definition of done already answered, which is the entire point of an increment.