With the modern URLs in v10 we have introduced the ability to add parameters to the URL.

Imagine a page with a variant that uses 'attributes' to sell the variant in different colors and sizes.

Traditionally the URL might have looked like this: 

www.yourdomain.com/p-3-bike.aspx

The URL would land the shopper on a page where he or she could select size:

With today's modern URL structure, your URL will look like : www.yourdomain.com/product/3/bike ...

... but now you can add your conditions as parameters.

So, if you send a shopper an email with an attractive hyperlink, you can link them to 

www.yourdomain.com/product/3/bike?size=large&color=red

or

www.yourdomain.com/product/3/bike?color=blue

or

www.yourdomain.com/product/3/bike?variantid=4

​If you are 'feeding' products to Google and Bing, you will know that this is a fabulous advance - you can feed the red product, and the blue product (that might have different images, and/or different PRICES) and the shopper will land on exactly the right combination of attributes.
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