[Tex/LaTex] How does \textit work

fontsitalic

I want to know: how does \textit commands work? Does it use a different font (italic shaped font)? Or is it just a pure LaTeX command that changes text shape to italic?

My main problem: How to make a backward it-shaped text?

Best Answer

Nothing I'd do, but, with XeLaTeX or LuaLaTeX,…

\documentclass{article}
\usepackage{fontspec}

\newfontface{\backitshape}{lmroman10-italic}[
  Extension=.otf,
  FakeSlant=-0.4,
]
\DeclareTextFontCommand{\textbackit}{\backitshape}

\begin{document}

Some text \textit{in italic} and \textbackit{backwards tilted italic}

\end{document}

enter image description here

Your title question is easy to answer: \textit chooses a different font.