Dock
The row of application icons along the screen edge that NeXTSTEP introduced in 1989 and macOS made famous — half launcher, half list of what is running.
NeXTSTEP placed the Dock as a vertical column of tiles along the right edge, with the NeXT logo at the top and the Recycler at the bottom. Each tile was an application; the ones not running showed three dots in the corner. Dragging an application into the Dock was the entire installation, and a click launched or switched. Documents did not belong there but on the Workspace Manager's shelf, a deliberate split that Apple later abandoned.
Mac OS X moved the Dock to the bottom in 2001, let it hold documents and minimised windows, and gave it magnification and the genie effect — to the dismay of Bruce Tognazzini, whose list of reasons it was bad became almost as well known as the Dock itself. On the X side, AfterStep had already cloned the idea as the Wharf in 1996 and Window Maker in 1997 as a dock with its own dockapps, and GNUstep carries the original forward. In 2009 Windows 7 let the taskbar pin programs, at which point the difference between a dock and a taskbar effectively disappeared.