Heraldry
Heraldry is the knowledge and art of describing coats of arms, also referred to as achievements or armorial bearings. Its origins are in the need to distinguish participants in battles or jousts and to describe the various devices they carried or painted on their shields.
However it is important to note that a given coat of arms is defined by a written description (which is given in heraldic language, called "blazon"), not by a picture. A given coat of arms may be drawn in many different ways, all considered equivalent, just as the letter "A" may be printed in many different fonts while still being the same letter. For example, almost invariably the shape of the shield is immaterial and different artists can depict the same coat of arms on many different shapes of shield.
A description of a coat of arms is called a blazon. To draw it is to emblazon it. To ensure that the pictures people draw after reading the descriptions are accurate, and reasonably alike, blazons follow a set of rules. The first thing the blazon describes is the tincture (colour) of the field (background) (though in some cases of "landscape heraldry" all or part of the field is some sort of landscape), and then it describes the placement and tinctures of the different charges (objects) on the shield. The charges on a shield are described from the top to the base, from dexter to sinister. Dexter ("right" in Latin) is the left side of the shield, and sinister ("left") is the right, as seen by the viewer. The reason for this is that they refer to the shield-bearer's point of view, not the observer's.
There are no strict definitions of the shades of colours used in Heraldry.
The word "crest" is commonly used to refer to a coat of arms. However, in heraldry, a crest is just one component of a coat of arms. In a complete depiction of a coat of arms, the crest is a design affixed to the helmet. However, crests can also be used on their own; this is particularly useful when there is insufficient space to display the entire coat of arms.