It is a lower-bound on the cost of erasing a bit. Reversible computing retains enough information to run the computation backwards, resulting in the erasure of no bits.
> On the other hand, recent advances in non-equilibrium statistical physics have established that there is no a priori relationship between logical and thermodynamic reversibility.[19] It is possible that a physical process is logically reversible but thermodynamically irreversible. It is also possible that a physical process is logically irreversible but thermodynamically reversible. At best, the benefits of implementing a computation with a logically reversible system are nuanced.[20]
The idea of a logically non-reversible, physically reversible process blows my (admittedly layman) mind. But, the paper Wikipedia linked to on that topic was around 100 pages, so any understanding will have to wait…
