Master resale rights enable you to resell the product to your customers along with the basic resell rights that come with it. Your customer in turn can also resell the product to their own customers, some products come with "non-transferrable Master Resale Rights" whic means you may sell the product to your customers but not the Master Resale Rights, our customer may resell the product with resale rights only..

Note:different rights depending on the developer so it's important to thoroughly check each license prior to use,to understand exactly how you can modify your product and resell it.