This gland is sometimes called the master endocrine gland because it controls all the other endocrine organs in the body. ADH stimulates the kidney to reabsorb water. The more ADH there is in the blood the harder the kidney works to reabsorb water. When a hormone has had an effect on its target organ the process of negative feedback can switch the endocrine organ off. Here is a simple analogy to help you understand negative feedback.
Positive feedback is the reverse of negative feedback.
When we are having an arguement, we do not really listen to each other. If I raise my voice to make you listen to me, you react by raising your voice. We still don't listen. We start to get angry. I throw a pot at you and you throw one back.