As has been said, Type 1 diabetics have a non-functioning pancreas which doesn't produce any insulin, thus they require injections of insulin to survive. Type 2 Diabetics have a fully functional pancreas that produces a normal amount of insulin but their body is resistant to the effects that insulin has, sometimes it can be helped by diet alone but some people require medication for their bodies to become less resistant to the insulin. There is also people who produce less insulin to which they are resistant so require both the tablets to reduce this resistance and extra insulin to prevent the high glucose associated with lower quantities of insulin.
There are other differences, but they are more complex. Also please note, Type 1 Diabetes is not just diagnosed in Childhood or as a Young Adult, you can develop it at any time in your life, and Type 2 is not just for older people, there are now significant numbers of much younger people who are developing T2. The old ideas to do with age being related to what type of Diabetes you get have been out dated by these facts.