The website, bgoodoffer24.com, is not a Microsoft authorized reseller of Windows activation keys. Some websites sell volume license keys which are meant to be used with multiple keys, but they can be invalidated at any time and are not legal. So, be careful of where you get your licenses or you'll risk facing problems down the line. Those volume license keys may work for a month or so, may not work, or have expired.
Only Amazon (not the marketplace section) and Microsoft itself are authorized to sell digital downloads. The website, bgoodoffer24.com, is likely reselling MSDN licenses. MSDN or TechNet Product keys are genuine Microsoft product keys, they are actually retail licenses, but it is intended for a particular product channel, either the Microsoft Software Developer Network (MSDN) or TechNet for IT Professionals who pay a subscription fee. But, the main purpose is for evaluation.
The great thing about licenses, unlike trial Microsoft software, MSDN or TechNet keys don't expire. Because the agreement under which the subscription is provided is a single license, none of the software should be distributed outside of it, and should only be used for one person and no one else. Unfortunately, regardless of the licensing terms, persons still abuse the program, they either giveaway product keys or resell it on auction sites. Microsoft licenses it in good faith that customers won't do so, but I guess human nature wins out.
But, once Microsoft detected that these keys are being abused, they will block them from further use, which will cause them to stop working. This why it is recommended that you purchase genuine licenses from the Microsoft Store.