The majority of physical products come with personal use only, but digital items may have rights that allow you to sell or even change parts of the product before you sell it on. I always recommend you read the license details that come with each product, but I will give you some general terms and uses here.
Personal Use (PUO)
When you purchase or get given a product that is declared as personal use only then it means exactly what it says. Your product rights are the right to read or use the product and not pass it on to anyone else. If the product is graphic based then you can use the graphics in a book you have written or on a website that you own. There are many graphics and templates or headers that you can use for your own website(s).
Resell Rights (RR)
When you are given or purchase resell rights to a product that means you have permission to sell that product. You may be asked to sell the product at a set price or a price not lower than a set amount. You can not pass on the resell rights to your customers. You must sell the product with personal use only (unless it specifically states otherwise in the license). You will usually have permission to change the sales page and to put your name on the sales page as the seller.
Master Resell Rights (MRR)
Master resell rights means you have product rights to sell the product and to pass on those rights to your customers. The majority of products with master resell rights allow you to pass on the master rights to your customers but read the license that comes with the product thoroughly to ensure that is the case. I have come across MRR product rights that only allow you to pass on resale rights and not master resell rights. As with the resell rights products you will generally have permission to change the sales page.
Private Label Rights (PLR)
This can be one of the most complex type of product rights that you will come across. Unfortunately you will have to read the accompanying license very carefully to ensure you stay within the rights allowed. Generally private label rights mean you can make any changes you want to the document including the title. You can sell the document, either the revised edition or the original, but in a lot of cases you cannot pass on the private label rights but you can pass on the master resell rights. If you change more than 80% of the document you can also claim copyright, but be careful as the new document should bear no resemblance to the original document. You can put your name as author even if you sell the document as is.
Unrestricted Private Label Rights (UPLR)
If you are lucky enough to obtain the unrestricted product rights then it means exactly what it says. There are no restrictions as to what you do with the document including passing on Private label rights to your customers.