Think of them as two different ways the body's sugar regulation system can go wrong.
Type 1 Diabetes: This is an autoimmune disease. Your immune system, which normally fights off harmful invaders, mistakenly attacks and destroys the insulin-producing beta cells in your pancreas. As a result, your body makes very little or no insulin. People with type 1 diabetes need to take insulin every day to survive. It's often diagnosed in children and young adults, but it can occur at any age. Scientists believe it's triggered by genetic factors and environmental exposures.
Type 2 Diabetes: This is much more common and usually develops over many years. In type 2 diabetes, your body either doesn't make enough insulin or your cells become resistant to the insulin that is produced (insulin resistance). This means the "key" (insulin) isn't working as effectively to let glucose into your cells. Initially, your pancreas might try to make extra insulin to compensate, but eventually, it can't keep up, and blood sugar levels rise. Lifestyle factors like being overweight, inactive, and having a family history of type 2 diabetes significantly increase the risk.