How to add meta tag in symfony3?

I want to add meta tags to my Symfony application.

How to use Meta Tags with Symfony 2.0
Twig change meta data
https://symfony.com/doc/current/cmf/bundles/seo/twig.html.
These links can't help me find out the correct answer.

This is my code. My page where I need to add the tag. Say "about.html.twig"

{% extends 'AppBundle::layout.html.twig' %}

{% block body %} 
.
.
.
{% endblock %}

I wanted to know which one to use.

{% block meta %}{% endblock %}

(or)

{% block metadata %}{% endblock %}

(or)

{% block head %}
    <head>
        <meta charset="UTF-8" />
{% endblock %}

Solution

meta or metadata or head are only the names. (not a statement) You can choose any name for this.

for example

base.html.twig

<!doctype html>
<html lang="en">
{% extends 'AppBundle::layout.html.twig' %}
  {% block title %}Title Website{% endblock %}
    <meta charset="UTF-8" />//////Repeat on all pages
    <meta http-equiv="content-language" content="fa,en">//////Repeat on all pages
  {% block metaTag %}
      <meta name="{{ description }}" content="Your description">
  {% endblock %}

{% block body %}

{% endblock %}