Overview
The coat of arms of the United Kingdom are the arms of dominion of the British monarch. They are both the personal arms of the monarch, currently King Charles III, and the arms of the state. In addition to the monarch, the arms are used by state institutions including the Government of the United Kingdom, the Parliament of the United Kingdom, and the British judiciary. Differenced versions of the arms are used by members of the British royal family. The monarch's official flag, the Royal Standard, is the coat of arms in flag form.
There are two versions of the coat of arms. One is used in Scotland, and includes elements derived from the coat of arms of the Kingdom of Scotland, and the other is used elsewhere and includes elements derived from the coat of arms of the Kingdom of England. The shields of both versions of the arms quarter the arms of the kingdoms of England and Scotland, which united to form the Kingdom of Great Britain in 1707, and the Kingdom of Ireland, which united with Great Britain to form the United Kingdom in 1801. The Irish quarter now represents Northern Ireland, after the partition of Ireland in 1921.
The present arms do not include a represention of the United Kingdom's fourth constituent country, Wales, primarily because the country was conquered by England by 1283 and later formed an integral part of the Kingdom of England. Wales is instead represented heraldically by two royal badges, which use the Welsh dragon and the coat of arms of Llywelyn ab Iorwerth respectively.
Description
From Wikipedia (CC BY-SA 4.0).