In summary, the E-Cat is a cold fusion (CF) device (the inventor, Andrea Rossi, prefers to term the technology “Low Energy Nuclear Reaction” which appears to be the same thing as CF but a less contentious phrasing). I’ll refer you to my Network World column for a more long-winded explanation of the background and theories about the device.
The problem with Rossi’s system is that it is too good to be true. It is claimed that the E-Cat only requires some initial heating to start after which the reaction is self-sustaining. The reaction uses a secret catalyst to transform nickel into copper with heat being produced which can be used to make steam, drive a Stirling engine, or be used for whatever you please.
If this device works as claimed, the world will change and not just a little but hugely and at every level of how we’re organized, how we make stuff, how we travel, and how wealth is distributed. And those changes won’t just impact the US or the Western hemisphere; they will transform the entire world because incredibly cheap energy is the ultimate game changer.