It is possible to hide or show different parts of your template according to the current page being accessed using Liquid Tags. You can create Contextual Sections within any template file; for instance, to create a Contact Us Section on the Main Layout, you can use something similar to this code:

{% if on_show_question_page %}
  <!-- content for question page -->
{% elsif on_index_page %}
  <!-- content for index page -->
{% elsif on_contact_us_page %}
  <!-- content for contact page -->
{% elsif category != null %}
  <!-- content for category page -->
{% else %}
  <!-- content for thanks page -->
{% endif %}

Here is a complete example on how to create a custom navigation section only on the Index Page:

{% if on_index_page %}
  <ul id="navigation">
    {% for categories on roots_categories %}
      <li><a href="{{ categories.url }}">{{ categories.name }}</a></li>
    {% endfor %}
  </ul>
{% endif %}

One another example is to list the Top Questions:

{% if on_index_page or on_question_page %}
  <ul id="top_questions">
    {% for questions in top_questions | limit: 5 %}
      <li>
        <a href="{{ questions.url }}">{{ questions.name }}</a>
        <p>{{ questions.description }}</p>
      </li>
    {% endfor %}
  </ul>
{% endif %}

Check the Shopify/Liquid Documentation to ‍view the complete list of Liquid Objects and Syntax and the Standard Sections‍ to view the Standard Sections references.