Cut refers to the finish and proportions, and how these factors influence the overall appearances of a diamond.
White and contrasted light called "brilliance" the colour flashes called "fire" and "scintillation" or flashes of light that occur when the stones moves, the ratio of weight vs. size, the smoothness and the symmetry of polished faces: all these determine how light enters the stones, in what it returns to the eye, and how the stone performs in terms sparkles. The cut grade is expressed on a scale from Excellent to Poor.
Heart and Arrows:
Also called H&A, these are mostly round diamonds with a superior cutting quality. They display a visual pattern of 8 hearts when looking at the same pavilion, and 8 arrows when viewing the stone in the face-up position, while using a Hearts and Arrows loupe.