Most diamonds have tiny imperfections called inclusion. Many inclusions are too tiny to be seen by anyone other than a trained diamond grader. The clarity range is ranged from Flawless (perfect inside out) to Included (visible to naked eyes). The less visible the inclusion and the clarity level will be higher.
The color evaluation of most gem-quality diamonds is based on the absence of color. These distinctions make a very big different in diamond quality. The less color and the color grade will be higher, where color grades range from D to Z. (D is colorless and Z is tinted yellow or brown.)