I'm sure somewhere or another you've heard of the 4 C's. But just in case you've been living under a rock for the past few years or even a decade, here they are:
Cut, in this instance, refers to the shape of a diamond.
Many people get confused with carat and size. The carat actually refers to the weight of the diamond.
1 carat is divided into 100 points like a dollar is made of 100 pennies. That is why sometimes you will hear jewelers refer to a half-carat, 0.50ct, as a 50 pointer.
It's funny to think that diamond color grading is based of how colorless a diamond is. The color scale ranges from D to Z, D being the highest grade and Z being the lowest grade. It's easy to remember because the word "diamond" start with "D" and the rest just goes down the alphabet.
Clarity is graded by the visibility of the inclusions (inside the diamond) and blemishes (outside the diamond) or identifying characteristics a diamond has. You can think of this characteristics like fingerprints or snowflakes. No two diamond have the same exact inclusions. Diamonds are grade using 10x magnification.
That's just a brief overview of the 4C's and the first steps to understanding diamonds.