I'm trying to find out what the difference is between the grains used for all grain brewing/mashing and the special grains used during the first part of extract brewing.
In AG brewing you are extracting all of the sugars from the grains, so you will use a bunch of 'base' grains, like 2 row, + the special grains, which can add flavor/color to the wort.
In PM brewing you are using the extract to replace the base grains, and using the special grains to add to the flavor/color profile.
Well, they are different in the way they are made. Take crystal, for example. It's wetted and kilned. This process actually changes the starches into sugars, and some of the sugars become unfermentable. So, you can't use it as a basemalt (not that you'd want to anyway) because you wouldn't get much fermentable sugars out of it. It does give color, flavor, and sweetness to beers and that's why it's used. Because it's processed, it does not need to be mashed, so it's good for steeping, as well as all-grain brewing. Some "specialty" grains that are used, though, can also be mashed (or even need to be- like flaked corn) and that's where it gets confusing.
Ahhh. This is from the wiki....
Understanding the processes by which individual types of grain are created will help the brewer use those grains intelligently. However, for extract home brewers, the most important distinction between the different types of grain is whether or not the resulting
The distinction it most likely refers to is whether or not a grain requires mashing. The malts chart on the wiki provides a quick reference to see which that applies to.