Vexillology is the study of the history, symbolism and use of flags. Someone who studies flags is known as a vexillologist, while someone who designs flags is a vexillographer. Vexillographers are often members of heraldic organizations, using their heraldic knowledge to create meaningful flag designs. If you simply like or enjoy flags, you are a vexillophile.

The term is more recent than you might expect, coined by in 1957 by Whitney Smith, a famous exponent of the art. It is derived from the Latin vexillum, meaning both a flag hung vertically from a spear and a group of men under a flag.

A big part of vexillology is the study of historical flags, and the analysis of the symbols and colors used in them. For instance, many flags bear a remarkable number of similarities, as in the case of the flags of the Scandinavian nations which bear version of the Nordic Cross in different colours. Red, white, and blue appear in the flags of many former English colonies to reflect the Union Flag, while flags of Muslim nations often integrate green, a colour associated with Islam.

The International Federation of Vexillological Associations (FIAV) is an international federation dedicated to "the creation and development of a body of knowledge about flags of all types, their forms and functions, and of scientific theories and principles based on that knowledge." It holds a biannual conference and publishes scientific papers on the subject.

In the UK, Vexillilogical interests are managed by the charity, The Flag Institute, of which Zephyr is a founding member.

There are specific technical terms that relate to the components and flying of a flag. Here are the main ones:

A coat of arms or simple heraldic symbol, such as a shield or crest.

Any quarter of a flag, but commonly means the upper hoist (left) quarter, such as the field of stars in the flag of the United States.

A figure or symbol appearing in the field of a flag.

a device often used as a charge on a flag. It may be heraldic in origin or modern, for example the maple leaf on the Canadian Flag.

The background of a flag; the color behind the charges.

A narrow edging or border, often in white or gold, on a flag to separate two other colours. For example the white and gold lines of the South African Flag.

the half or edge of a flag farthest away from the flagpole. This term also sometimes refers to the horizontal length of a flag.

The half or edge of a flag nearest to the flagpole. This term also sometimes refers to the vertical width of a flag.

the span of a flag along the side at right angles to the flagpole.

the span of a flag down the side parallel to the flagpole.