VTE syntax is basically split between two things: Tags and Expressions.

<title> {{ title }} </title>
{% for user in users %}
<li> {{}} </li>
{% endfor %}

1) Expressions are delimited by "{ { variable_name } }" and they are used to print data.

2) Tags are delimited by "{ % tag_name % }" and they are used to express intents like loops, conditionals, etc.

There are many default tags and you can create your own too by adding an extension, you can also customize the markers so instead of "{%" you could use "#[" or whatever do you think it's best.