Twig is the main templating engine used not only by Symfony but now Drupal 8. Wait, a templating engine! But why?
Twig helps you easily manipulate template data while subtly encouraging you to handle all non-trivial logic elsewhere. It’s also super easy to start using productively. It includes plenty of features such as embeds, includes, macros and more which allow you to build powerful templates quickly that can be easily maintained.