Like it's been said, carbon is a cloth. There are many varieties of carbon based on the application needed. Different thicknesses and weaves are available depending on what you need. Carbon is similar to any other composite, as it gets it's strength from the bonding of fiber and resin (under pressure for optimum).
Carbon really shines vs. fiberglass in that it can achieve excellent strength characteristics when it is combined with the correct ratio of resin, and held under pressure to force the bonding. For non structural/visual parts, hand layup is acceptable. This involved layering each piece of cloth and applying the resin by hand (resin total based on weight of cloth). This is not ideal, because there will be a higher saturation of resin on the cloth, which will weaken the composite piece. Now, there are some variations on this, one is called vacuum bagging. Instead of trying to force the carbon cloth to conform to the curves and changes of the mold (almost impossible for any semi-complex part), the composite is wetted with resin in the mold, and then placed in a special bag. The part is then held under vacuum, which forces the cloth to conform to the shapes of the molds evenly. This doesn't address the issue of resin ratio though. A bleeder layer is used to soak up excess resin, but it's still not as good as other methods.
Prepreg is the most commonly used method in structural, high performance applications. This is what F1 teams use in the construction of their tubs, and the body of the McLaren F1 to name a few. Instead of the fabirc (dry) and the resin (wet) being combined at the time of product creation, the resin is "impregnated" into the cloth when the cloth is made. This creates the optimum ratio of cloth to resin, as the application of resin can be strictly monitored. The problem is that the resin isn't a liquid, more like a powdered plastic of sorts that has been infused with the cloth. In order for it to actually set, it must be held under pressure and heat. That's where the autoclaves come in (which are pressurized ovens). They hold the part (which is under vacuum in the bag, similar to the above) under pressure in the oven, which causes the resin to actually "melt and fuse" in a way, it releases the resin and causes it to set. The result is a part that is both light weight and very strong, depending on the number of layers and type. The only drawback is autoclaving parts is very expensive. The prepreg is also very expensive, and has a shelf life to it.
A new method has been gaining popularity. It's called resin infusion. This is what I did to all my parts. It's a hybrid method of vacuum bagging. Instead of laying a wet piece of cloth in the mold and holding under vac, only the dry carbon is held under vacuum. Once under vacuum, a feed line of resin is inserted into the bag and the resin is pulled from the reservoir into the mold. The cool thing is that only the amount of resin needed to fill the void and wet the cloth is used under vacuum. What that means is that you get a part that is damn near the weight and strength of prepreg without the high overhead. For 90% of the applications that a street-going car would ever see, prepreg would be overkill. Body components are not stress members, and do not carry much load. So, spending a fortune for prepreg vs. resin infusion doesn't make sense.
I can get into more specifics of anyone is interested
James