TLDR: cutting a zillion microcavities in the (inside) bottom of a metal pot improves the heat transfer from the metal to the water & steam. Which means you don't need the bottom of the pot (or outside of the boiler tube, or etc.) to be quite as hot, for a given steam output.<p>In thermodynamics theory, or on an industrial scale, this improves the efficiency.<p>If you're just cooking spaghetti, or dreaming of perpetual motion machines - "sorry, move on".