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.
Since sometime around Plasma 4, KDE has been the name of the organization and Plasma had been the name of the desktop.