unresolved
A graph this build could not construct, because no provider claimed its type when the project loaded -- typically an addin that is absent or disabled. The track runs a substitute graph, and these carry the original definition verbatim so that saving writes it back rather than replacing it with the substitute.
Both are empty for every track whose graph did load, which is how a UI tells "this track is running what the project asked for" from "this track is standing in for something this build cannot make".