What is Windows 8 core?

Solution 1:

Windows 8 (Core) is simply Windows 8. It's the base (core) product, which Pro and Enterprise built on.

And I say that because I can find no official reference to a Core product and it was in parenthesis in your source (compared to the other editions where no parenthesis was used).

Solution 2:

The "Core" from "Windows 8 Core" simply emphasizes it is the "plain" Windows 8 and not one of the other versions (Pro, Enterprise, RT).

Paul Thurrott of WinSuperSite explicitly names Windows 8 Core in his giant comparison table of different Windows 8 editions (notice the plain "Windows 8" is absent from the table because it is referred to as "Core"):

More information about the different editions of Windows 8.

Solution 3:

It means the "Home" edition for all intents and purposes. Perhaps the best source for this is MSFT's own site (for Windows programmers). Search for "PRODUCT_CORE" here (which programmers rely on) and look at the "Meaning" column:

https://msdn.microsoft.com/en-us/library/windows/desktop/ms724358(v=vs.85).aspx

Note that it currently refers to it as "Windows 10 Home" but all other editions have their own qualifiers (e.g., search for "PRODUCT_PROFESSIONAL", "PRODUCT_ENTERPRISE", etc.) In fact, prior to the release of Windows 10, the "Meaning" column for "PRODUCT_CORE" (at the same link) referred to it as simply "Windows 8", which normally means the home edition by default (in the absence of the terms "Pro", "Professional" or "Enterprise").