\parindent & \parskip ¶Synopsis:
\setlength{\parindent}{horizontal len}
\setlength{\parskip}{vertical len}
Both are rubber lengths (see Lengths). They affect the
indentation of ordinary paragraphs, not paragraphs inside
minipages (see minipage), and the vertical space between
paragraphs, respectively.
For example, if this is put in the preamble:
\setlength{\parindent}{0em}
\setlength{\parskip}{1ex}
The document will have paragraphs that are not indented, but instead are vertically separated by about the height of a lowercase ‘x’.
In LaTeX standard class documents, the default value for
\parindent in one-column documents is 15pt when the
default text size is 10pt, 17pt for 11pt, and
1.5em for 12pt. In two-column documents it is 1em.
(These values are set before LaTeX calls \normalfont so
em is derived from the default font, Computer Modern. If you use
a different font then to set \parindent to 1em matching
that font, put
\AtBeginDocument{\setlength{\parindent}{1em}} in the
preamble.)
The default value for \parskip in LaTeX’s standard document
classes is 0pt plus1pt.