Oats are the whole grains that are the seed of the oat plant. Whole oats are usually unprocessed after they are harvested, they undergo a cleaning and roasting process, though the covering of the oats strips away in this process but retains the nutrients and fiber, making it as one of the healthiest food.
Oats are gluten free and have low glycemic index with many minerals like manganese, phosphorus, magnesium, copper, iron, zinc, folate, vitamin b1, vitamin B5, making it even more healthier. Oats are good source of carbohydrate and fiber with protein and some amount to fat as well.
There are two definition for oatmeal, 1. when oat is cooked then its known as the oatmeal. or 2. when the oat grains are processed or the outer covering is stripped they are also known as the oatmeal.
Though there are three types of oatmeal, the rolled oats and instant oats are mostly known. The differences between these two oats depends on the processing of the oat.
Rolled oats are flat flakes which are husked and crushed then rolled, whereas instant oats are the most processed one, they are pre-cooked, dried, rolled and then pressed slightly thiner than the rolled one.
The third variety of oat is known as the steel-cut oat, these are the course oats they look like broken wheat, with a chew texture. The cooking time is more than the rolled and instant oats. You may need to soak it for few hours before cooking.