Carbon parts are usually made with either of two different processes.

The first method uses carbon fiber cloth and liquid resin, and is usually done as wet layup (more on that later) or vacuum infusion. I won't get into the differences there, but just know that wet (liquid) resin is applied to carbon fiber cloth.

The second process uses carbon fiber that is already impregnated with resin. The liquid resin is applied to the carbon fiber using a machine with rollers, and the amount of resin is very tightly controlled (more on that later). Then a sheet of masking is applied to both sides, and the impregnated carbon is frozen to keep the resin from curing until it is used. Carbon of this type is called "prepreg" because it's pre-impregnated with resin. It's taken out of the freezer, warmed up to room temp, masking sheets pulled off, and applied to the mold. It's tacky and feels almost like the vinyl sheet that stickers are made of, but the resin isn't a goopy liquid so the aftermarket industry started calling it "dry carbon".

Okay, so now to tie the two processes together. It's hard to control the amount of resin for the amount of carbon fiber when making parts, so the strength to weight ratio isn't as good as it could be. With prepreg parts, the amount of resin is very tightly controlled so the strength to weight ratio is much better. There are also consistency benefits and other stuff I won't get into.
Anyway, that's why prepreg parts are usually used for most strength- and weight-critical applications. And for expensive non-critical street car parts, oddly enough.

The aftermarket industry calls prepreg parts "dry carbon" parts though, because although the carbon is completely covered with resin, the resin isn't in goopy flowing liquid form when it is applied. They're trying to differentiate lower quality parts made by wet layup processes from the more expensive prepreg parts. So apparently the street car aftermarket thinks that "prepreg" is too much of a mental tax to remember, and they've made up their own wording that no one else in the composites world uses.

I consider "dry carbon" to be carbon fiber cloth with no resin applied. You start with dry carbon, you apply resin, then the resin cures and makes a part. You can't make carbon parts with no resin, therefore you can't really have "dry carbon" parts.