can someone explain the clarity of a diamond to me?

my mother wants to buy an engagement ring, round brilliant, M color and VVS1 clarity. But she wants to know why the increase in costs between a VVS1 and VS1? she wants to know what is really clear and how to get the clarity of a diamond, decide on what the ring is VS1 and the ring is VVS1. Also if you have any place (except Tiffany & Co), where I could buy a ring, please include the information in your message.

Try http://www.bluenile.com/diamonds/diamond-clarity link to the Blue Nile. You can also buy diamonds there, but it is line. Your information is very large diamond.

Round Brilliant Three Stone Diamond Engagement Ring 14k

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