There are auto-immune and non-auto-immune types of diabetes.
Auto-immune is where the body attacks its own beta cells. In children and some adults this tends to happen very quickly and the person becomes very ill and requires immediate insulin - Type 1. In many adults, it happens over a long or very long period of time and progression to requiring insulin can be quick or slow depending on a number of factors - LADA. Do NOT make the mistake of believing anyone presenting with diabetes over the age of 35 is Type 2 - use diagnostic tests GAD antibody and c-peptide to differentiate - it's important to prognosis, follow-up and ultimately to selecting the appropriate treatment.
Non-autoimmune is where the body produces but cannot effectively use its own insulin - Type 2. Reducing insulin resistance is usually initially the most effective treatment - low-carb diet, exercise, weight loss - these can often stop Type 2 progressing - it does not cure it.
There are other, less common, genetic types of diabetes - MODY - these should be considered where there is family history of genetic types of diabetes, where the person is not auto-immune (rule that out first), where risk factors for Type 2 are missing or where the person does not respond as expected to Type 2 treatments.
That's what I would teach them in a nutshell.
Smidge