CLARITY

Because diamonds formed deep within the earth, under extreme heat and pressure, they often contain unique birthmarks, either internal (inclusions) or external (blemishes). Diamonds without these birthmarks are rare, of course rarity affects a diamond's value. Using the International Diamond Grading System, created by GIA which contains 11 clarity grades, diamonds are given a clarity grade that ranges from flawless (FL) to diamonds with more obvious inclusions (I3). In the picture below, the red lines symbolize inclusion and blemish in each grades.

FL (Flawless) 
No inclusions or blemishes are visible to a skilled grader using 10x magnifications

IF (Internally Flawless)
No inclusions and only blemishes are visible to a skilled grader using 10xmagnification

VVS1 and VVS2 (Very, Very Slightly Included)
Inclusions are difficult for a skilled grader to see under 10x Magnification

VS1 and VS2 (Very Slightly Included)
Inclusions are clearly visible under 10x magnifications but can be characterized as minor

SI1 and SI2 (Slightly Included)
Inclusions are noticeable to a skilled grader using 10x magnifications

I1, I2, and I3 (Imperfect)
Inclusions are obvious under 10x magnification and may affect transparency and brilliance