\documentclass[a4paper]{article}
\usepackage{lmodern}
\usepackage{amssymb,amsmath}
\usepackage[T1]{fontenc}
\usepackage[utf8]{inputenc}
\usepackage{babel}
\usepackage{hyperref}
\begin{document}
\thispagestyle{empty}
\parbox{.7\linewidth}{
\section*{Spaces}
\subsection*{Normal spaces only:}
Thin spaces are used in abbreviations and before units, e. g., 10 s.
Normal-width non-breaking spaces can help keep honorary titles and names on one line: Dr. Fooboar.

\subsection*{Different spaces:}
Thin spaces are used in abbreviations and before units, e.\,g., 10\,s.
Normal-width non-breaking spaces can help keep honorary titles and names on one line: Dr.~Fooboar.

\subsection*{French spacing:}
\frenchspacing
Thin spaces are used in abbreviations and before units, e.\,g., 10\,s.
Normal-width non-breaking spaces can help keep honorary titles and names on one line: Dr.~Fooboar.
}

\end{document}