Type 1 - Where the pancreas produces little or no insulin, this is dangerous and can kill them. They can control it by having a controlled diet but also have to inject insulin into the blood at mealtimes
Type 2 - Where the person is resistant to insulin (their body cells don't respond to the hormone), this can cause blood sugar level to rise to a dangerous level. Type 2 is controlled by avoiding foods rich in simple carbohydrates (like sugars) which increase glucose levels.
(I'm sitting this exam aswell)