It’s always been just KDE to me. In the past year or so, I’ve noticed people calling Plasma KDE or even just Plasma. What happened? Why do people insist on making the name longer? Why the word Plasma? What is Plasma referring to? And, are they trying to move away from the KDE name to just Plasma?
Answer: Plasma is the desktop environment. KDE is the community that makes Plasma and many other related software.
I have no idea about the history behind this but I assume it has to do with the abbreviation DE being inside KDE. I could see how that makes people think that KDE is the DE, and not the community that develops Plasma.
The issue is that it was the DE originally, some people (myself included) just didn’t fully get the memo when it changed like 15 or so years ago. I haven’t used the KDE DE since before that change, so I get how it could be missed. Rebranding is hard, even years later. I am sure many people think KFC still stands for Kentucky Fried Chicken too.