\documentclass{article}

\begin{document}
A simple equation \verb|\frac{a}{b}|
\begin{displaymath}
\frac{a}{b}
\end{displaymath}
A simple equation with additional space \verb|\frac{a} {b}|
\begin{displaymath}
\frac{a}
 {b}
\end{displaymath}

\section [Section without space]{A new section title without space}

\section [Section with space] {A new section title with space}

\end{document}

