HiFi uses the Twig Templating Language.  For those that aren't familiar with it, Twig is a modern PHP templating language that takes much of its inspiration from Django templates.  Twig looks like this:

Printing a variable

{{ var }}


{% for post in posts %}
  {{ post.title }}
{% endfor %}


{% extends "layout.html" %}
{% block content %}
  Content of the page...
{% endblock %}

Twig is easy and clean and is a good match with HiFi's overall philosophy. Be sure to check out the template selection section so that you can know which templates are chosen when your site is visited through different urls.