In TeXForm#
TeXForm parses this entry as a character leaf mapped to U+21D4 (LEFT RIGHT DOUBLE ARROW).
\to\rightarrow\longrightarrow\mapsto\xrightarrow\Rightarrow\Leftrightarrow\leftarrow\longmapsto\hookrightarrow\Longrightarrow\implies
\LeftrightarrowSymbol
The ⇔ symbol (Left right double arrow, U+21D4), written as \Leftrightarrow in LaTeX math mode.