You are permitted to resell the product to your customer in order to make a profit, but your buyers are not allowed to resell it to their customers. Basically, you cannot claim authorship, change it in any way or add resell rights to the product, for these products are designed to sell onto buyers who want to use it for themselves without redistributing and giving someone else the ability to sell the specific product.
Master Resale Rights – MRR
MRR rights make it possible for you to resell the product along with the basic resell rights that come along with it, meaning your customer will be able to sell the product to his/her customers as well. MMR products are more favorable for prospects would like to be able to distribute the product among themselves in order to make money or gain from it. MRR rights are similar to Resell Rights and you are not allowed to claim authorship or change the product in any way.
Private Label Rights – PLR
PLR rights not only allow you to buy the product, but also give you the ability to change it in any way you want to. A PLR product can basically be treated as if you had created it yourself as the author, along with the resell rights; however you are not allowed to claim the copyright on the product.
Buying PLR would always be a good investment, BUT be sure to read the license agreement beforehand, for some PLR products will still have restrictions forbidding certain actions like giving the product away for free or changing the content itself. Branding rights are confused with PLR nowadays and some products will only allow you to brand the product with your own affiliate links, nothing more.