How Flask-Bootstrap works?
<p>I'm learning Flask web development, and the tutorial I'm following introduces an extension called <strong>Flask-Bootstrap</strong>. To use this extension, you must initialize it first, like this:</p>

<pre><code>from flask_bootstrap import Bootstrap
# ...
bootstrap = Bootstrap(app)
</code></pre>

<p>Weirdly enough to me, the variable <code>bootstrap</code> is not used in the rest of my module. However, if I comment out this line, a <code>jinja2.exceptions.TemplateNotFound</code> exception will be raised. Also, the templates used start with this line:</p>

<pre><code>{% extends "bootstrap/base.html" %}
</code></pre>

<p>But I don't have a directory named <code>/bootstrap</code> under <code>/templates</code>!</p>

<p>I want to know what's going on:</p>

<ol>
<li>What does the <code>bootstrap = Bootstrap(app)</code> line do?</li>
<li>Where does <code>bootstrap/base.html</code> reside? </li>
</ol>