@item SHELL
The name of an interpreter used to parse and execute programs run from
inside Emacs.
+@cindex background mode, on @code{xterm}
@item TERM
The name of the terminal that Emacs is running on. The variable must be
set unless Emacs is run in batch mode. On MS-DOS, it defaults to
@samp{internal}, which specifies a built-in terminal emulation that
-handles the machine's own display.
+handles the machine's own display. If the value of @env{TERM} indicates
+that Emacs runs in non-windowed mode from @code{xterm} or a similar
+terminal emulator, the background mode defaults to @samp{light}, and
+Emacs will choose colors that are appropriate for a light background.
@item TERMCAP
The name of the termcap library file describing how to program the
terminal specified by the @env{TERM} variable. This defaults to