There are a few different types of diabetes that doctors refer to and also the ones that are not clinical.  Here is a short list of the different types and my take on each.

Pre Diabetes – Refers to the period before developing diabetes where the blood sugars are higher than normal, but not high enough to classify as diabetes.  The ADA defines pre diabetes as one who has a fasting blood glucose of 100-125 mg/dl.  Those with a fasting blood glucose greater than 125 mg/dl are classified as having diabetes.

Type 1 diabetes (may also be referred to as: Insulin Dependent or Juvenile onset) makes up a small percentage of the overall number of people with diabetes at around 5%
Type 1.5 or referred to as Latent Autoimmune Diabetes in Adults (LADA) due to the late onset of diabetes that is not typical of T1
Type 2 diabetes, (may also be referred to as: Adult onset or non-insulin dependent) is more prevalent and makes up nearly 90% of diabetes cases
Type 3 (not a clinical type of diabetes) or commonly referred to as the person(s) taking care of someone with diabetes or diabetes community

Gestational Diabetes is fairly common and impacts nearly 1 in 5 (18%) expecting mothers.  My non technical explanation is that an expecting mother’s body can become resistant to insulin and require up to 3x as much insulin as before pregnancy.  It is a very serious condition because the high blood sugars can affect the unborn baby.  For more information, check the ADA site.