[From the Italian intaglio, ‘carving’] in sculpture the term denotes a hollow or negative design which is usually cut into a hardstone or metal die that, when pressed or stamped onto a soft substance, gives an impression or a positive relief, for example on early Mesopotamian cylinders. In printmaking, intaglio refers to all metal-plate processes, such as engraving and etching, in which the recessed areas which have been created and then inked are printed from (as opposed to the raised areas of relief printing or the flat surface adhesion of planography).
What is printmaking?
Printmaking is the process of making artworks by printing, normally on paper. Printmaking normally covers only the process of creating prints that have an element of originality, rather than just being a photographic reproduction of a painting. Except in the case of monotyping, the process is capable of producing multiples of a same piece, which is called a print. Each print produced is not considered a "copy" but rather is considered an "original". This is because typically each print varies to an extent due to variables intrinsic to the printmaking process, and also because the imagery of a print is typically not simply a reproduction of another work but rather is often a unique image designed from the start to be expressed in a particular printmaking technique. A print may be known as an impression. Printmaking (other than monotyping) is not chosen only for its ability to produce multiple impressions, but rather for the unique qualities that each of the printmaking processes lends itself to.
From Wikipedia
http://www.moma.org/interactives/projects/2001/whatisaprint/print.html
Relief Printing
relief
[From the Italian rilevare, ‘to raise’] a sculpture made so that all or part of it projects from a flat surface. See LETTERPRESS; WOODCUT.
Intaglio Printing
intaglio
Planographic Printing
planography
A term used to describe a surface technique of printmaking, such as lithography or screenprinting, as opposed to relief or intaglio where the surface of the printing plate or block is cut into or incised.