Diabetes means that your PANCREAS does not make enough INSULIN. The Pancrease is a gland in your body. Sugar is a fuel used by the body to give you energy and make you feel well. The main sugar in the body is GLUCOSE. Glucose needs to get into the cells in your body to give you energy.
Insulin is like a key (click to see animation); it opens the door to the cells in your body and allows the glucose to enter. So, insulin lowers the level of glucose in your bloodstream.