E-books, software, articles and other written, raw materials are just some examples of products where you can obtain Private Label Rights.
Take an E-book, for example. If an author of an E-book sold you Private Label Rights about "Cellular Phone Technology", you could modify the content to tackle the latest developments about this ever-changing technology.
You can add features and create helpful sub-topics that would best fit the current trends in cellular technology.
After the modifications, you can claim rights to the e-book that you modified.
The idea may have been copied or bought, but you get to have the rights to resell the "new" product resulting from the one that was modified.