Epsom salt
Bath salts or Epsom salt are things that people add to the water when they take a bath.  Some bath salts have things to make the water smell good.  Some bath salts have medicines in them. Epsom salt, or magnesium sulfate, is made of magnesium, oxygen and sulfur.  It is named after the town in England where people first learned to use it.  Sometimes people call things that are not Epsom salt "bath salts" too, if they are meant to be thrown into a bath to make the water feel or smell good.