A:Answer Tl;dr - The more expensive one is the retail version. The less expensive one is the OEM version. The retail version can only be installed on one computer at a time, but can be uninstalled and reinstalled on any computer. The OEM version is cheaper because it can only be installed ONCE to ONE computer. It cannot be reinstalled.
The one that costs $199.99 is the retail version of Windows 10 Pro 64 Bit. The one that costs $142.99 is the OEM version. The OEM version is cheaper because there are disbenefits to this version as opposed to the retail version. The OEM version is a one-time use Windows license. It can only be installed on one computer, one time. If you were to uninstall the OEM version, you cannot reinstall it; not even on the same computer it was uninstalled from. The retail version can't be installed on multiple computers either. Unlike the OEM version however, the retail version of Windows CAN be reinstalled on any computer, so long as it is only installed on one computer at a time.
For more information, I'd recommend reading this article before deciding whether or not it's worth it to buy the less expensive OEM version:
http://www.worldstart.com/windows-10-oem-vs-retail-whats-the-difference/
Hope this helps!