LaTeX is a language for creating structured documents. One of the most important ways of creating structure in a document is to split it into logical sections. If your document deals with more than one concept or theme, then each concept should go into its own section.
There are two related commands for creating sections:
\section{sectiontitle} and \section*{sectiontitle}. The
first one numbers the sections, while the starred form does not. Both
create separate sections with titles in a larger font size; they also
provide information to LaTeX in case you want to create a Table
of Contents.
Practice:
Create a document with five numbered sections.