Cut of course is just simply the cut of the diamond. Does she like a round diamond? A princess cut, perhaps....certainly the rage for today's modern bride. How about a pear shape or a marquise cut? You can even get an oval, heart or some other exotic cut not part of the mainstream.
Color is a scale that helps define the overall body color of a diamond. D, E, F are colorless ranges. G, H, I are the white ranges. And J, K, L start the yellow ranges. There are other diamonds that go into the fancy color ranges like Canary, Champagne, and Cognac up to the much, much rarer blues and the extremely rare reds. In today's world, color can be imparted onto diamonds such as a surface diffusion treatment or the entire diamond body color can be changed through irradiation. Not necessarily a bad thing but a thing that must be disclosed to you the buyer. A whopping 99% stay with the D through L range - predominately in the G,H,I. and that's pretty much where you want to stay, too. Typically, a diamond is never enhanced in these ranges either.
Clarity defines the internal inclusions and or surface blemishes that a diamond may have under 10 x (power) magnification. This is actually FTC defined. These inclusions are uncrystallized diamond or carbon seen as tiny black spots in the diamond itself or they can be white like gas or air pockets or they can even be tiny fractures called feathers. Obviously, a feather is not a huge crack that goes from side to side across the diamond. That would be someone else's stone, not yours.