A sidebar is a short piece of text, rarely longer than a single column or page, that is presented outside the narrative flow of the main text.

Sidebars are often used for digressions or interesting observations that are related, but not directly relevant, to the main text.

abstract, blockquote, epigraph

<article xmlns='http://docbook.org/ns/docbook'>
<title>Example sidebar</title>

<section><title>An Example Section</title>

<para>Some narrative text.
</para>

<sidebar><title>A Sidebar</title>
<para>Sidebar content.
</para>
</sidebar>

<para>The continuing flow of the narrative text, as if the
sidebar was not present.
</para>

</section>

</article>