What's dehydration and overdehydration? how are they treated?

Plenty of fluids: Dehydration occurs when someone does not drink enough fluids to keep up with the body losses and or needs. For exemple, as we breathe, urinate and pass stools, we are loosing liquids. Our body is smart and stimulate thirst , so we drink. Sometimes sickness overcomes our abilities , exemple if someone has severe diarrhea and vomiting and cannot drink enough.