As explained on the directory structure page, the /_posts folder is where your blog posts will live. These files are generally Markdown or HTML. All posts must have YAML Front Matter, and they will be converted from their source format into an HTML page that is part of your static site.
Creating Post Files
To create a new post, all you need to do is create a file in the /_posts directory. Jekyll requires blog post files to be named like these:
All blog post files must begin with YAML Front Matter.
To improve the user experience for both reading and writing posts, TeXt made some enhancements for markdown and some additional styles.
YAML Front Matter
--- layout: article title: Document - Writing Posts mathjax: true ---
Between these triple-dashed lines you can set variables. you can consider it as page configuration, these would overrides the global configuration in _config.yml.
Beside Jekyll’s predefined variables, TeXt define some new variables for each layouts, see Layouts for details.