A face is a named collection of graphical properties: font,
foreground color, background color, background pixmap, optional
underlining, and (on TTY devices) whether the text is to be highlighted,
dimmed, blinking, or displayed in reverse video. Faces control the
display of text on the screen. Every face has a name, which is a symbol
such as default or modeline.
Each built-in property of a face is controlled using a specifier, which allows it to have separate values in particular buffers, frames, windows, and devices and to further vary according to device type (X or TTY) and device class (color, mono, or grayscale). See Specifiers, for more information.
The face named default is used for ordinary text. The face named
modeline is used for displaying the modeline. The face named
highlight is used for highlighted extents (see Extents). The
faces named left-margin and right-margin are used for the
left and right margin areas, respectively (see Annotations). The
face named zmacs-region is used for the highlighted region
between point and mark.