To create the table of contents is straightforward, the command \tableofcontents does the job. Sections, subsections and chapters are included in the table of contents. To manually add entries, for example when you want an unnumbered section, use the command \addcontentsline as shown in the following example:

\documentclass{article}
\usepackage{blindtext}
\usepackage{titlesec}
\title{Sections and Chapters}
\author{Gubert Farnsworth}
\date{ }
\begin{document}

\maketitle

\tableofcontents

\section{Introduction}

This is the first section.

\blindtext

\addcontentsline{toc}{section}{Unnumbered Section}
\section*{Unnumbered Section}

\blindtext

\section{Second Section}

\blindtext
\end{document}

This example produces the following output:

Example table of contents produced in LaTeX

Change the title of the table of contents

The default title for the table of contents is Contents; it can be changed into whatever you need as the following example demonstrates:

\documentclass{article}
\title{Sections and Chapters}
\author{Gubert Farnsworth}
\date{ }
\renewcommand*\contentsname{Summary}
\begin{document}
\maketitle
\tableofcontents
\section{Introduction}
   
This is the first section.
      
Lorem  ipsum  dolor  sit  amet,  consectetuer  adipiscing  
elit.   Etiam  lobortisfacilisis sem.  Nullam nec mi et 
neque pharetra sollicitudin.  Praesent imperdietmi nec ante. 
Donec ullamcorper, felis non sodales...
       
\addcontentsline{toc}{section}{Unnumbered Section}
\section*{Unnumbered Section}

Lorem ipsum dolor sit amet, consectetuer adipiscing elit.  
Etiam lobortis facilisissem.  Nullam nec mi et neque pharetra 
sollicitudin.  Praesent imperdiet mi necante...

\section{Second Section}
       
Lorem ipsum dolor sit amet, consectetuer adipiscing elit.  
Etiam lobortis facilisissem.  Nullam nec mi et neque pharetra 
sollicitudin.  Praesent imperdiet mi necante...
\end{document}

Open this example in Overleaf

This example produces the following output:

Changing name for table of contents in LaTeX

The line \renewcommand*\contentsname{Summary} will write "Summary" instead of the default value. If you are using the package babel for international language support, the aforementioned command must be placed inside the braces of

\addto\captionsenglish{ }

Instead of English in \captionenglish write the name of the language you set in babel.

Table of contents

Introduction

Change the title of the table of contents

Further reading