Excellent explanation, indeed, but with one (common) error:

If you have a one pound weight bolted to the floor, and try to lift it with one pound of force (or 10, or 50 pounds), you will have applied force and exerted energy, but no work will have been done.

One will have 'exerted' no energy. Energy is work (or ability to perform work), not force. Only when the weight is actually lifted against the force of gravity, work is performed and energy spent (or, more precisely, transferred to weight, which can spend it by, say, smashing something upon fall).

Sorry for nitpicking .