Wikipedia
Xinerama is an extension to the X Window System that enables X applications and window managers to use two or more physical displays as one large virtual display.
Developed under the name PanoramiX by Madeline T. Asmus of the Digital Equipment Corporation's Unix X Server Engineering Group, the software was contributed to The Open Group for X11 Release 6.4 (X11R6.4) and renamed Xinerama. It was then incorporated into the XFree86 4.0 release in 1998 and the Solaris 7 11/99 release. According to X Server project lead Rob Lembree, the name was inspired by the Cinerama widescreen theatre process. "We were frustrated by having big Alpha machines with multiple displays, and being unable to move applications from one to another. It was developed as much out of frustration as out of competitive advantage." Xinerama advantages include the ability to only maximize windows to the dimensions of the active physical display, and to allow new pop-up windows on the active physical display.