Leeneia, the foot dealies are an springy extender that makes the wearers legs more efficient. They are spring loaded by the flexible bar you see bending under the wearers shoe. Professional models have gas pistons to return even more energy into each step.
Running in them makes you super-fast.The downside is that if you trip, you'll probably faceplant so hard you'll have to be extracted from the ground with a backhoe.
I've seen videos where folks do all manner of bizarre acrobatics wearing them...such as jumping high over a car with a somersault at mid-leap.
If you added these to standard basketball the hoops would need to be raised about 15 more feet to make it a sport again.