Diabetes is a disease where the body cannot properly produce or use insulin, resulting in high blood sugar levels. There are three main types of diabetes: type 1, type 2, and gestational diabetes. Type 1 is an autoimmune disease where the body destroys the cells that produce insulin. Type 2 develops due to insulin resistance and lack of exercise and overweight/obesity often contribute to risk. Gestational diabetes only occurs during pregnancy. Symptoms vary but include excessive thirst, hunger, and urination. Treatment involves monitoring blood sugar, exercise, diet, and medications like insulin or metformin depending on the type of diabetes.