Salt nic was invented by juul. It gives u a stronger cigarette like initial buzz vs freebases which is more of a constant level.
Salts r smoother than freebase, qllowing for much higher levels, but r really intended for high ohm, low vapor devices, like q juul.
U can use them in a regular subohm, u just have to use q lower strength then used for a little pod because u r cunsuming much more nicotine into your blood with salts vs freebase (for the first 20 min). Then they both pretty much drop to the same level.
Some would argue that the initial buzz from salts makes it more addictive than freebase for the exact same reasons cigarettes are.
Salts have q higher incident of qllergies to certain brands of salts (different ones use different reactants to turn freebase into salt)
Also, some would say freebase is cleaner qnd purer then salts. While i like the benefits of salts personally (smoother, stronger, longer shelf life), i dont really disagree, freebase is straight nicotine, for better or worse, as harsh as it is, thats how it is unadulterated)