KDE and GNOME are the mainstream desktop environments for GNU/Linux. There are lightweight options that use fewer resources, such as Xfce or Fluxbox, but new users are more likely to encounter KDE or GNOME, which most closely follow the familiar desktop metaphors common to Windows or Mac.
The historic challenge for the KDE and GNOME developers has been to reproduce the functionality available to users of other operating systems, and a bit more besides. But in recent times the developers have begun to look towards a future that might take the desktop further beyond the accepted conventions.
As the KDE developers have expressed it: "Desktop computing has changed radically in the last 20 years, yet our desktops are essentially the same as they were in 1984. It's time the desktop caught up with us."
The point and click desktop as we know it has been around since monitors had flickering green screens, although the average laptop has disk, RAM and graphics capacity that was undreamt of a few short years ago.
The approach of both GNOME and KDE developers is to find ways of taking full advantage of both the expanding technology and the limited spacial characteristics of the modern computer screen. In doing this they have to satisfy the conflicting demands of users.