PVD is a process, DLC is one of the coatings applied using that process. PVD= physical vapor deposition, basically using plasma to vaporize the coating material, and electrostatic charge to plate that vapor to the material surface. edit: little mistake, it's not exactly electrostatic charge, rather the coating is vaporized via plasma and then somehow they "bombard" the part to be coated with the vapor. Titanium nitride, DLC, Boron Carbide, are all PVD coatings. DLC = diamond like carbon, which is a pretty accurate description, it's not quite diamond but is made primarily of carbon and has similar molecular structure/hardness. Most of the time I see DLC referred to as Tungsten DLC, so I assume tungsten is part of the process somewhere but haven't found out whether it's a pre-coating plating, or if it's actually part of the DLC itself. DLC and boron carbide are probably the hardest of the PVD coatings you'll see on a regular basis.
Gonna have to defer to fred for the answer to that, but most likely it's a black colored titanium nitride finish over a polished satin. PVD coatings are generally so thin they take on the finish of whatever they were applied to. Bead or sandblasted items give a matte appearance, and mirror polished items will retain that appearance.
All of the PVD's I'm familar with are extremely hard, harder than glass or steel. Their biggest weakness is the material they're applied to, if you hit it with something that can dent or gouge the base metal then the coating will often be damaged too. If you're familiar with the way a good hard anodize wears, the pvd will have similar behavior, but generally better wear resistance. Most of the time when someone is complaining about a scratch or mark on something with a PVD coating it's actually metal from another object that's embedded into the finish, kind of like a piece of chalk on a chalkboard. One interesting thing, at a bodycote presentation back in 2000 or 2001 someone in the audience asked if there was anything chemical that could damage these finishes. The owner replied that they did have some issues in bathroom faucets. Some folks were getting hydrogen peroxide on them, likely from bleaching their hair or something, and they discovered that it can attack some of the titanium nitride finishes over time.