Your diamond will have a clarity rating that is based on the number and type of inclusions inside the diamond. Inclusions are nature's birthmarks in the diamond. While the diamond crystal is growing and forming these marks are what make your diamond unique and not like any other gem. Each diamond will have different types of inclusions. The number and type of inclusions make up the Clarity Scale. The scale is based on using a jeweler's 10x loupe for magnification.
The scale starts at 'Flawless'. This means that the outside and the inside of the diamond is completely free of inclusions. This is incredibly rare, in fact, less than 1% of mined diamonds will qualify for a 'Flawless' rating. 'Internally Flawless' is next, meaning that the diamond's insides are completely free of inclusions. Again, this is incredibly rare.
Next on the scale is 'VVS1 and VVS2'. This stands for Very Very Slightly Included. Diamonds with this rating will have very small inclusions that are incredibly hard to see with magnification. The 1 and 2 designations are for the two levels of the category. The VS1 rating is higher, and therefore those diamonds will have fewer inclusions than the VS2 designation. These diamonds are also very rare.
Next we have 'VS1 and VS2'. This stands for Very Slightly Included. These diamonds will have slightly more visible inclusions but still only visible with magnification.
On to 'SI1 and SI2'. This stands for Slightly Included. These diamonds will generally not have visible inclusions in the SI1 category but may have in the SI2 category. These diamonds provide a great value as most of the time the inclusions are not visible to the naked eye but because they are less rare the cost goes down.
Finally, we have 'I1, I2, and I3'. This stands for Included 1,2 and 3. These are diamonds that have very visible inclusions and can sometimes detract from the beauty of the diamond. Each diamond is different, however, and sometimes these diamonds can provide a very beautiful look for a very desirable price.