Diabetes is when your pancreas doesn't make enough insulin or stops making insulin at all. To simplfy it you could just say that diabetes is when something is wrong with your pancres.
Type 1 diabetes is a chronic condition in which your pancreas makes little or no insulin at all.
Type 2 diabetes is when your body doesn't make enough insulin or becomes resistant to insulin that is present.
The way you get type 1 diabetes is through genetics. Like say one of the parents has type 2 diabetes and have a child, the child has a chance of developing type 1 in the future.
Anyone can get type 2 diabetes. You can get type 2 diabetes by not taking care of yourself or your body. You gain too much weight and your pancreas might fail and then you will get type 2 diabetes.
It can identify prediabetes, which raises your risk for diabetes. It can be used to diagnose diabetes. And it's used to monitor how well your diabetes treatment is working over time. It's also a critical step in forming your game plan to manage diabetes with your diabetes care team.