Whats the difference between type 1 diabetes and type 2?

Hi everyone.
My boss just found out her 16 year old daughter has type 1 diabetes. We were all very sad to hear the news. Apparently she will be taking medication everyday for the rest of her life and she has a strict diet to follow. What's the difference between type 1 and type 2? Also, do people with diabetes have a tendency to be thin and lose a lot of weight because of their diet? Apparently before she was diagnosed, she lost 10 pounds within a month.

Thanks!