It is a truism that you never understand anything unless you can understand it more than one way. I like this one:
When he and his colleagues spun ClearMotion out of the Massachusetts Institute of Technology in 2008, their intention was to use bumps in the road to generate electricity. They had developed a device designed to be attached to the side of a standard shock absorber. As the suspension moved up and down, hydraulic fluid from the absorber would be forced through their device, turning a rotor that generated electricity. But, just as a generator and an electric motor are essentially the same, except that they run in opposite directions, so ClearMotion’s engineers realised that running their bump-powered generator backwards would turn it into an ideal form of suspension. And that seemed a much better line of business. They therefore designed a version in which the rotor is electrically powered and pumps hydraulic fluid rapidly into and out of the shock absorber. The effect is to level out a rough road by pushing the wheels down into dips and pulling them up over bumps.