This character is a Other Symbol and is commonly used, that is, in no specific script.
The glyph is not a composition. Its East Asian Width is wide. In bidirectional text it acts as Other Neutral. When changing direction it is not mirrored. U+1F451 offers a line break opportunity at its position, except in some numeric contexts.
The CLDR project calls this character โcrownโ for use in screen reading software. It assigns these additional labels, e.g. for search in emoji pickers: clothing, family, king, medieval, queen, royal, royalty, win.
This character is designated as an emoji. It will be rendered as colorful emoji on conforming platforms. To reduce it to a monochrome character, you can combine it with Variation Selector-15: ๐๏ธ See the Emojipedia for more details on this characterโs emoji properties.
The Wikipedia has the following information about this codepoint:
A crown is a traditional form of head adornment, or hat, worn by monarchs as a symbol of their power and dignity. A crown is often, by extension, a symbol of the monarch's government or items endorsed by it. The word itself is used, particularly in Commonwealth countries, as an abstract name for the monarchy itself (and, by extension, the state of which said monarch is head) as distinct from the individual who inhabits it (that is, The Crown). A specific type of crown (or coronet for lower ranks of peerage) is employed in heraldry under strict rules. Indeed, some monarchies never had a physical crown, just a heraldic representation, as in the constitutional kingdom of Belgium.