I'm no expert, but in both salt and potassium chloride, it's chloride (rather than chlorine, the element), i.e. the Cl- ion.
In (say) tap-water, I believe it's a very weak dilution of Cl2, the molecule of the elemental form, i.e. a dissolved form of chlorine gas, which is nasty stuff, as used in World War I (I believe - just checked, and they did use chlorine, but there were others as well).
That's just my guess.
However, there is no denying that we need chloride, e.g. as part of HCl - hydrochloric acid - stomach acid, so it plays a valid part in our body.
This is not true (so far as I know) of fluoride, bromide or bromate.
Anyway, I've ordered it (after reading discussions in old posts here). The interesting question is what is the ideal potassium to sodium ratio:
I did some fairly extensive googling on this the other day, and could not find any hard and fast answer. A lot of guesses, but no convincing "answer".
I've made a rough estimate myself based on a kind of average of what I read, but there is no point in my stating it here, because it's just my guess and no better than anybody else's. And you can all use google just as well as I can.
For what it's worth, from my calculations (actually a molecular weight calculator I found on the web) if you take equal weights of salt and potassium chloride, taken together, you are getting very slightly more weight of potassium over sodium. In a K:Na ratio of about 0.52:0.47.