ELI5 Version: Your body uses sodium and electrolytes to lead water molecules around like a dog on a leash.
Too much salt and you have too many leashes and not enough dogs for them. Your body will make you thirsty and ask for more dogs to walk with all those empty leashes. Too much water and it’s chaos because you have too many dogs and not enough leashes, so your body will have to let some dogs go. (You pee out the extra water for the environment to wrangle instead.)
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