X Window System (X.Org) infrastructure
x11-common contains the filesystem infrastructure required for further
installation of the X Window System in any configuration; it does not
provide a full installation of clients, servers, libraries, and utilities
required to run the X Window System.
.
A number of terms are used to refer to the X Window System, including "X",
"X Version 11", "X11", "X11R6", and "X11R7". The version of X used in
Debian is derived from the version released by the X.Org Foundation, and
is thus often also referred to as "X.Org". All of the preceding quoted
terms are functionally interchangeable in an Debian system.