Types of Oats

I'm starting to experiment with recipes based on oats, inspired by the discovery that a little oatmeal in split pea soup makes for a smooth, unctuous texture (with no oatey flavour or texture). Turns out there are loads of grinds for oats that make a big impact on what you can do with them. I need a list of definitions to refer to until I become more familiar with the different kinds.

Oat groats are simply the whole grain, unprocessed except to have the tough outer skin removed. Think of brown rice.

Pinhead oats, Steel-cut oats, Coarse oatmeal, or Irish oatmeal, cracked groats, milled to varying coarseness: Pinhead (coarse or rough oatmeal, Low GI); Medium (most common in Scottland, 1 to 2mm in diameter, Low GI); Fine oatmeal or Oatmeal flour (not exactly interchangeable as the former still has the bran, Medium GI).

Rolled Oats, Jumbo, Old fashioned, Porridge oats, Flaked oats, (sometimes Quick oats or Quick Cook), where the groat is steamed then rolled flat to make a flake. Medium GI.

Instant Oats have been cooked longer and, because of the extra processing, is considered High GI.