Clarity is basically inclusions in diamonds. Clarity can be categorized as following, Flawless (FL), internal flawless (IF), very very slight inclusions (VVS), very slight inclusions (VS) , slight inclusions (SI) and lowest clarity scale id Inclusion (I).
It is near to impossible to have a diamond without impurities. Diamonds without inclusions or blemishes are rare. Often invisible to the naked eye, these natural blemishes are categorized as – inclusions, which are internal, and blemishes, which are external. When the stone was being formed sometimes trace elements or minerals get trapped that result in inclusions that appear as feathers, clouds or crystals. Scratches and chips visible to the naked eye are known as blemishes.
FL, IF:Flawless, Internally Flawless. There are no inclusions – internal flaws – or blemishes – external flaws.
VVS1, VVS2: Very, Very Slight Inclusions. Hard to view such inclusions under 10x magnification. An excellent quality diamond.
SI1, SI2: Slight Inclusions. Inclusions are visible under 10x magnification and may not be visible to the naked eye when the stone is in the face-up position.
I1, I2, I3: Included: Inclusions are obvious under 10x magnification and may affect transparency and brilliance. I1 diamonds have inclusions that are almost always visible to the naked eye.