How do I tab (indent) a paragraph in LaTeX?

LaTeX will automatically indent the first line of each paragraph that doesn't immediately follow a section heading. If you'd like to get rid of an indent, you can use the \noindent command:

\section{Introduction}
This is the first paragraph.

\noindent This is the second paragraph.

If you'd like to indent the first paragraph after a section heading, you can include the indentfirst package in your preamble:

\usepackage{indentfirst}

The amount by which the first line of a paragraph is indented is controlled by a parameter command called \parindent. For more information, and examples, refer to the Overleaf article on paragraph spacing.

If you'd like to indent a whole paragraph, various techniques are described in this post on the TeX StackExchange forum and this Overleaf help article