It's a package for specifying and rendering fully-parametric three-dimensional models.
No one does blueprints anymore. We all do them as parametric solids that can be assembled, organized into machines, break-tested, etc. etc. It's incredible what can be done all inside a computer now. And when you're done, it goes straight to my five-axis thingy and we cut one right out of the material of your choice!
You can instead send it to a 3D printer, but those parts aren't nearly as strong -- unless you've got one of those sexy titanium printers. That's next on my Christmas list.