Rhett: No one ever asks what electrolytes are.  Does anyone even ever ask?

Hank: Electrolytes! They are ions.  It's just a fancy word for ions.  So you got sodium, potassium, chlorine, magnesium, calcium, I think those are the big five that you need to not die, and they are super important.  Basically, so like, just think of yourself as a big bag of water and lots of good chemistry is happening in that water to keep you not dead.  That water is a little bit salty, like not as salty as the ocean, but it's a little bit like--you have tasted your tears before. 

Now I'm picturing Rhett crying and I'm sad, but I'm--we all cry.

Those ions are ridiculously important to our lifestyles, but that's not important here.  When we talk about electrolytes in like sports drinks, the idea is that the drink is roughly as salty as the body that it's going into, and of course, you lose a lot of ions when you sweat.  It's part of the mechanism of how you sweat, so these sports drinks are supposed to be replacing those ions though, unless you're sweating a lot.  Doesn't matter.