Checking for the existence of a field value in Twig
Twig syntax is new for most Drupalists, and learning how to check for the existence of a field value is a valuble skill for anyone building a Drupal 8 theme. For example, consider the case where there is an optional text field called "Photo caption" on a content type. If the content author populates the "Photo caption" field, then it should be output as follows:
<figcaption>{{ content.field_photo_caption }}</figcaption>