Those little pieces of code are used to insert a Related Posts and Recent Posts column to Jekyll Bootstrap site. Just put them any where you want it to display in the post template (usually /_includes/themes/theme-name/post.html).

<h4>Related Posts</h4>
<ul>
  {% for post in site.related_posts limit:5 %}
  <li><a href="{{ BASE_PATH }}{{ post.url }}">{{ post.title }}</a></li>
  {% endfor %}
</ul>

Recent Posts

<h4>Recent Posts</h4>
<ul>
  {% for post in site.posts limit:5 %}
  <li><a href="{{ BASE_PATH }}{{ post.url }}">{{ post.title }}</a></li>
  {% endfor %}
</ul>	

Note: Replace limit:5 with the number of posts you want to display.

Demo Image