What’s "project relationship"?

When you have projects that depend on each other, Jenkins can track which build of the upstream project is used by which build of the downstream project, by using the records created by the fingerprint support.

For this feature to work, the following conditions need to be met:

1. The upstream project records the fingerprints of its build artifacts
2. The downstream project records the fingerprints of the upstream files it uses

This allows Jenkins to correlate two projects.