Etching and Relief
Etching (v) is a printing technique in which an etching needle is used to draw into a ground that is applied over a metal plate, the plate is then submurged in a series of acid baths which wear away at the metal surface that has been scratched away with the needle. The ground is removed and ink is then forced into the depressions and then printed. Often confused with engraving.
A relief (n) is an object or form that projects from the background, typically divided into three degrees, high relief in which the form is clearly seperated from the background, low relief in which there is a slight raise from the background, and sunken in which the backgrounds are not cut and the figure is the one which recedes into the distance.