It goes like this...
B Updates: They're the Patch Tuesday Updates.
"The big updates most people are familiar with come out on “Patch Tuesday,” the second Tuesday of the month. These are called “B” updates because they’re released in the second week of the month. That explains why there are no “A” updates, as Microsoft doesn’t generally release updates in the first week of the month.
B updates are the most important updates, featuring new security fixes. They also contain previously released security fixes from prior B updates and previously released bug fixes from prior C and D updates.
They’re the main, most important type of Windows Update. They’re also predictable for system administrators, who know when to expect them."
C and D Updates:
“C” and “D” updates are released in the third and fourth weeks of the month, respectively. These do not include any new security updates.
These updates just include new bug fixes and improvements for other non-security issues. Microsoft says C and D updates are “optional,” and Windows Update won’t automatically install them on your PC.
According to Microsoft, “D” updates typically include the majority of non-security updates. This gives people a few weeks to test them before those non-security fixes are released to everyone in the next B update. Microsoft sometimes releases “C” updates in the third week of the month for Windows 7, Windows 8.1, and older versions of Windows 10, which gives people more time to test them."
What really matters is when and how you update!
Windows Update doesn’t automatically install C and D updates on most PCs. However, it does install C and D updates when you head to Settings > Update & Security > Windows Update and click “Check for Updates.” In Microsoft’s world, this makes you a “seeker” who wants to test these updates before most Windows users get them. Microsoft disclosed this in a recent blog post.
So, if you click “Check for Updates” in the third, fourth, or first week of a month before the next B update has been released, you’ll probably get a C or D update installed on your system. If you never click “Check for Updates,” you’ll stick with the better-tested B updates.
All of the above is true. So help me. We've stepped through the mirror for sure, this time.
Sooo...now you know. B's on first, C and D are on third and fourth but only before B.
Sort of like "i" and "e" before "c"... but then, that's a different "c".
And with that I'll just say...
Oh yes...and if you have questions, refer to the article linked above.
Source:
https://www.howtogeek.com/398226/now-windows-10-has-c-b-and-d-updates.-what-is-microsoft-smoking/