Carbon fiber is a composite material (meaning it's made up of all kinds of stuff, and they talk about the carbon fiber because it's expensive). In model airplanes, I've seen carbon fiber used as part of the fuselage, as a way of adding tensile strength to butt joints, as engine mounts, as propellers... the list goes on and on. In every single use, the "carbon fiber" material behaves differently. Sometimes it has great compressive strength, sometimes it has great tensile strength, sometimes it handles heavy vibrating loads well, other times it fails in moments under those loads...

So a carbon fork could be doing any one of a number of things for the bike, and you don't know what is intended unless the manufacturer gives you *good* specs. Bike descriptions online often make it sound like they're going for the feel of a steel fork but with lighter weight. That doesn't mean that's what you'll actually get tho, unless they've got very good engineers. And well, good materials science types are Not Cheap. Neither is getting consistent results out of a composite.