Complete HubsPot Hubl Tutorial Guide
Hiding an Element Inside Page Editor Via HusBpot HubL
Basically the if statement allows you to show only an element inside the if statement.
What code says:
If the user doesn’t use the page editor, the post-body will wrap id called contents.
{% if is_in_editor %}
{{ content.post_body }}
{% else %}
<div id="contents">{{ content.post_body }}</div>
{% endif %}