[QBS] what about path magic variable?

[Smirnov Vladimir]

I have found such an example of Export Item:
(https://codereview.qt-project.org/#/c/103016/2/examples/app-and-lib/lib/lib.qbs) 

Export {
      Depends { name: "cpp" }
      cpp.includePaths: [path]
}

What is a "path" magic? it does not appear in Product item or Export 
item docs.
In Language introduction nothing too.
Where could I find info about it?