Dry carbon fiber and wet carbon fiber have to do with how the part is laid up.

Wet carbon fiber is essentially like fiberglass in that the weave has no resin in it. You wet the mold/part with resin, lay in the weave and then add additional resin and additional layers of weave if needed. Ideally the part is then vacuum bagged and put under pressure so that excess resin is squeazed out and the part is held firmly against the mold as the resin dries. This is how most people in their garages are covering interior parts.

Dry carbon fiber is frequently called "pre-preg". In this case the carbon fiber cloth is already impregnated with resin. The cloth is layed into a mold and each additional layer added as well. The part is then vacuum bagged and placed in an autoclave (a large pressurized oven). When heated the resin already present in the cloth melts and then wets into the fibers and between the layers of cloth. The resin then dries and you have a finished part.

The advantages of dry carbon fiber are that the amount of resin present is always correct since it's already in the cloth; there's never too little, too much or voids where there is no resin. This tends to make a lighter, stronger part with a better surface finish as well as hold much tighter tolerances in thickness. It also implies that the company making the parts is a bit more advanced in their design and engineering since it requires more specialized techniques and tools.

Honestly when talking about carbon fiber hoods, fenders etc none of this really matters. What counts most is the fit of the part and the quality of its finish. If you're building true carbon fiber structures that must carry loads (chassis, aerospace parts, etc) then there's no doubt that a dry lay up is superior.