This character is a Other Symbol and is commonly used, that is, in no specific script. The character is also known as basic symbol for speed limit.
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. If its East Asian Width is “narrow”, U+2B55 forms a word with similar characters, which prevents a line break inside it. Otherwise it allows line breaks around it, except in some numeric contexts.
The CLDR project calls this character “hollow red circle” for use in screen reading software. It assigns these additional labels, e.g. for search in emoji pickers: circle, large, o, red.
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: ⭕︎ See the Emojipedia for more details on this character’s emoji properties.
The Wikipedia has the following information about this codepoint:
Circle symbol may refer to (in ascending order of size, approximately):
˚, ring diacritic
◦, white bullet
∘, function composition
°, degree symbol
º, masculine ordinal indicator
o, music symbol denoting either a diminished triad or diminished seventh chord
o, superscript lowercase letter o
○, white circle Unicode symbol
◌, dotted circle
oοо, lowercase vowel letters in the Latin, Greek (omicron), and Cyrillic alphabets
𐤏, Semitic/Phoenician letter Ayin, the ancestor of the Greek, Latin, Cyrillic etc. letters
OΟО, uppercase vowel letters in the Latin, Greek, and Cyrillic alphabets