ELI5 Hard Water - is it a good or bad thing?

Why does soap not work with hard water? Is hard water a good or bad thing? What are water softeners? Why are they banned in some places? When you buy bottled water in plastic bottles, how come they have an expiration date? How can water expire? ... we explain like I'm five Thank you to the r/explainlikeimfive community and in particular the following users whose questions and comments formed the basis of this discussion: sn0rlaxftw, kittenrice, wyliecody, lustypad, th3hedonismbot, toxiclay, paravis and tokyojokeyo To the ELI5 community that has supported us so far, thanks for all your feedback and comments. Send us an e-mail: [email protected]