Hard water is basically regular water that picked up too much calcium and magnesium on its journey underground. It’s not dangerous to drink, but it’s a total nuisance for your home. Think of it as that friend who leaves a mess everywhere they go—harmless, but annoying.
These minerals don’t dissolve well, so they leave deposits behind. That’s why your shiny glassware comes out of the dishwasher looking cloudy and sad. Who wants to drink from a foggy glass?