The display screen is coated on the inside with a very thin layer of a phosphor (e.g. cadmium sulphide which gives out green light).
A layer of graphite (aquadag) painted on the inside of the vacuum tube is used to
(1) reduce the effect of negative-charge accumulation on the screen (this effect will reduce the brightness) and
(2) catch rebounding electrons that are back scattered from impact with the screen.
The graticule is the set of horizontal and vertical lines permanently scribed on the screen