Plasma is the KDE workspace. Actually it is a technology that can adapt to many types of devices. Currently there are two varieties of Plasma: The Plasma Desktop environment which is the focus of the majority of our pages and Plasma Mobile, the new cool environment for pads and smartphones.
An important part of Plasma are the "widgets". Widgets are the individual units of the desktop and they include (although they are not limited to) the application menu, icons, the system tray, the clock, etc. Widgets can exist on the desktop itself, or be inserted into the panel, on the screen saver or on the dashboard among other places. Widgets exist for a large number of tasks besides usual desktop helpers, including microblogging (Twitter, identi.ca), unit conversion calculators, weather forecasts, file sharing and much more. Panels and desktops are also special kinds of widgets themselves, meant to contain other widgets.