Relief is a sculptural technique. The term relief is from the Latin verb levo, to raise. To create a sculpture in relief is thus to give the impression that the sculpted material has been raised above the background plane. What is actually performed when a relief is cut in from a flat surface of stone or wood is a lowering of the field, leaving the unsculpted parts seemingly raised. The technique thus involves considerable chiselling away of the background, which is a time-consuming exercise with little artistic effect if the lowered background is left plain, as is often the case. On the other hand, a relief saves forming the rear of a subject, and is less fragile and more securely fixed than a sculpture in the round, especially one of a standing figure where the ankles are a potential weak point, especially in stone. In other materials such as metal, clay, plaster stucco, ceramics or papier-mache the form can be just added to or raised up from the background, and monumental bronze reliefs are made by casting.

There are different degrees of relief depending on the degree of projection of the sculpted form from the field, for which the Italian appellations are still sometimes used. The full range includes high relief (alto-rilievo), where more than 50% of the depth is shown and there may be undercut areas, mid-relief (mezzo-rilievo), low-relief (basso-rilievo, or French: bas-relief), and shallow-relief or rilievo schiacciato, where the plane is scarcely more than scratched in order to remove background material. There is also sunk relief, which was mainly restricted to Ancient Egypt. However the distinction between high relief and low relief is the clearest and most important, and these two are generally the only terms used to discuss most work. The definition of these terms is somewhat variable, and many works combine areas in more than one of them, sometimes sliding between them in a single figure; accordingly some writers prefer to avoid all distinctions. The opposite of relief sculpture is counter-relief, intaglio, or cavo-rilievo, where the form is cut into the field or background rather than rising from it; this is very rare in monumental sculpture.