The bulk of diamonds have tiny imperfections called inclusions. The less inclusions a stone has the cleaner it will be, thus allocated a higher clarity grade.
Clarity is often the least important of the 4Cs because most inclusions are microscopic; they don't affect the diamond's beauty in a visible way. Most diamonds with a VS2 clarity or higher are 100% eye clean. Si1 and Si2 clarity stones are fantastic value as they have inclusions that are hard to spot with the naked eye but are much cheaper than Vs or VVS stones.
To ensure you get the best stone possible every stone that is ordered is checked by us to ensure that the stone is eye clean, not cloudy and has no green/brown/yellow tinges.