As makers, I think we probably have the following two in common:
1. We like building stuff!
2. We have a 3D printer lying around somewhere.
While often #2 is seen as the perfect solution to #1, Root has some unique characteristics that can substantially increase a printer's usefulness to your project.
So, what is Root?
Root is a building system that consists of 3D-printable "blocks" that clamp around rigid shafting. 3D printed parts are very versatile and inexpensive, but weak - the shafting fixes this.
Root works the same way as a traditional building system like 80/20 extrusion would. Beams of varying lengths and gauges are assembled, and features are added along them: various actuator mounts, joints, linear sliders, sensors, wheels, rotary power transmission, and much more.
Root is useful in that printed parts can be stockpiled (jump right in to a new project, don't wait for your printer) and reused between projects. Also, no need to CAD!