
In my experience, Volume licenses are in their own "silo" and OEM licenses are in their own "silo". For instance, if you have an Office 2013 Pro Plus subscription license as part of an Office 365 E3 subscription, you can use that either for a click-to-run installer or an MSI installer from retail media. A key or license "silo" (my word for it) is a grouping of activation key and media/installer types that can be used interchangably. To make matters even worse, there are two primary installation types (MSI and click-to-run), and a few different key "silos".

The primary use of subscription licenses for Microsoft products for businesses today is through Office 365. They are activated by entering account information into the software that is connected with a licensed account online.

Windows 8 computers have the OEM activation built into the BIOS. Until Windows 8, OEM licenses included a sticker that was affixed to the computer that has a hologram and the activation key printed on it. You can also get Office or other Microsoft software with OEM licenses if you buy them bundled with a computer or server. When you buy a computer or server and you get Windows or Windows Server pre-installed, you are getting an OEM license.

Not necessarily related to the version or edition, there are several license types. The different flavors of one version, like 2012 R2 Standard, Datacenter, Essentials, or Foundation, are called "Editions" by Microsoft. The different generations of Windows Server, like 2003, 2008, 2012, are called "Versions" by Microsoft.
