Return value of build Pipeline step - What is it?

[George Sexton]

Can anyone help me understand what if any the return value is for the build pipeline step? I've read the docs here:

https://jenkins.io/doc/pipeline/steps/pipeline-build-step/#-build-%20build%20a%20job

There's a vague reference here:

propagate (optional)

If set, then if the downstream build is anything but successful (blue ball), this step fails. If disabled, then this step succeeds even if the downstream build is unstable, failed, etc.; use the result property of the return value as needed.

[Stuart Rowe]

The return value is a RunWrapper as long as wait is set to true.

[George Sexton]

Thanks.