Clarity difference in diamonds

Clarity is sometimes called purity. This terminology varies from grading lab to grading lab.
Let's discuss exactly what each clarity grade means. Diamonds in the flawless category are free from internal and external blemishes when examined by a skilled observer under 10X magnification (see below). Diamonds in the internally flawless category have no internal imperfections but some surface blemishes may be present.
The level of polish blemishes can be ascertained by reading the polish grade on Internally Flawless Clarity graded diamonds. Stones that have Flawless grade must grade Excellent for polish. Flawless graded diamonds are very uncommon, so its likely that this isn’t an issue for the average consumer.