Type 1 diabetes mellitus is an auto immune disorder in that pancreas is damaged and it can't produce any insulin.
Type 2 diabetic mellitus is a chronic condition, insulin is not adequately produced or utilised.
So in general in both the conditions glucose is not properly utilised with the help of insulin.
Type 1 will have produce quick onset of symptoms if untreated the petient will end up with ketoacidosis. Type 2 will be slower in producing symptoms but if untreated will lead to all micro and maro vascular complications.