Many Things. Type 1 diabetes usually starts in youth, up to the early 20's and almost always requires Insulin to treat. Type 2 diabetes, usually starts in middle age, may require Insulin to treat and is often treated with oral medications, but can sometimes be managed by diet, weight loss and exercise, all of which are often important in type 1 diabetes also.
Type 1. Requires Insulin to live type 2 can often be controlled with diet, exercise pills;sometimes need Insulin for better control, but won't pass away if no Insulin unless very poorly controlled.
Difference. The symptoms are not the issue but the cause is. Type 1 is a lack of insulin. You get ill right away with symptoms of increased appetite, thirst, urination and weight loss. You need Insulin to be replaced. Type 2 is a state of Insulin resistance. These symptoms take much longer to present. Insulin is present but the tissues do not respond as well. This can be handled with oral medication.