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+2658 forms with similar adjacent characters prevents a line break inside it.
The Wikipedia has the following information about this codepoint:
The knight (♘, ♞) is a piece in the game of chess, represented by a horse's head and neck. It moves two squares vertically and one square horizontally, or two squares horizontally and one square vertically, jumping over other pieces. Each player starts the game with two knights on the b- and g-files, each located between a rook and a bishop.
Representations
System
Representation (click value to copy)
Nº
9816
UTF-8
E2 99 98
UTF-16
26 58
UTF-32
00 00 26 58
URL-Quoted
%E2%99%98
HTML hex reference
♘
Wrong windows-1252 Mojibake
♘
Encoding: GB18030 (hex bytes)
81 37 AB 30
RFC 5137
\u'2658'
Bash and Zsh inside echo -e
\u2658
C and C++
\u2658
C#
\u2658
CSS
\002658
Excel
=UNICHAR(9816)
Go
\u2658
JavaScript
\u2658
Modern JavaScript since ES6
\u{2658}
JSON
\u2658
Java
\u2658
Lua
\u{2658}
Matlab
char(9816)
Perl
"\x{2658}"
PHP
\u{2658}
PostgreSQL
U&'\2658'
PowerShell
`u{2658}
Python
\u2658
Ruby
\u{2658}
Rust
\u{2658}
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