This character is a Other Symbol and is commonly used, that is, in no specific script.
The glyph is not a composition. It has no designated width in East Asian texts. In bidirectional text it acts as Other Neutral. When changing direction it is not mirrored. The word that U+25AD forms with similar adjacent characters prevents a line break inside it.
The CLDR project calls this character “hollow rectangle” for use in screen reading software. It assigns these additional labels, e.g. for search in emoji pickers: hollow, rectangle.
The Wikipedia has the following information about this codepoint:
Geometric Shapes is a Unicode block of 96 symbols at code point range U+25A0–25FF.
Representations
System
Representation (click value to copy)
Nº
9645
UTF-8
E2 96 AD
UTF-16
25 AD
UTF-32
00 00 25 AD
URL-Quoted
%E2%96%AD
HTML hex reference
▭
Wrong windows-1252 Mojibake
â–
HTML named entity
▭
Encoding: GB18030 (hex bytes)
81 37 9B 37
LATEX
\fbox{~~}
digraph
Or
RFC 5137
\u'25AD'
Bash and Zsh inside echo -e
\u25AD
C and C++
\u25AD
C#
\u25AD
CSS
\0025AD
Excel
=UNICHAR(9645)
Go
\u25AD
JavaScript
\u25AD
Modern JavaScript since ES6
\u{25ad}
JSON
\u25AD
Java
\u25AD
Lua
\u{25AD}
Matlab
char(9645)
Perl
"\x{25AD}"
PHP
\u{25ad}
PostgreSQL
U&'\25AD'
PowerShell
`u{25AD}
Python
\u25AD
Ruby
\u{25ad}
Rust
\u{25ad}
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