To start a paragraph, just type some text. To end the current paragraph, put an empty line. This is three paragraphs, the separation of which is made by two empty lines.
It is a truth universally acknowledged, that a single man in possession of a good fortune, must be in want of a wife. However little known the feelings or views of such a man may be on his first entering a neighbourhood, this truth is so well fixed in the minds of the surrounding families, that he is considered the rightful property of some one or other of their daughters. ``My dear Mr. Bennet,'' said his lady to him one day, ``have you heard that Netherfield Park is let at last?''
A paragraph separator can be made of a sequence of at least one blank
line, at least one of which is not terminated by a comment. A blank line
is a line that is empty or made only of blank characters such as space
or tab. Comments in source code are started with a % and span up
to the end of line. In the following example the two columns are
identical:
\documentclass[twocolumn]{article}
\begin{document}
First paragraph.
Second paragraph.
\newpage
First paragraph.
% separator lines may contain blank characters.
Second paragraph.
\end{document}
Once LaTeX has gathered all of a paragraph’s contents it divides that content into lines in a way that is optimized over the entire paragraph (see Line breaking).
There are places where a new paragraph is not permitted. Don’t put a
blank line in math mode (see Modes); here the blank line before the
\end{equation}
\begin{equation}
2^{|S|} > |S|
\end{equation}
will get you the error ‘Missing $ inserted’. Similarly, the blank
line in this \section argument
\section{aaa
bbb}
gets ‘Runaway argument? {aaa ! Paragraph ended before \@sect was complete’.