By following this tutorial, you've created a Markdown blog using the Slim Framework and PHP. The application uses the Standard PHP Library (SPL) to iterate over markdown files in the data/posts directory, filtering out non-markdown files with the `MarkdownFileFilterIterator`. It then aggregates the content from each file into an array of BlogItem entities, which can be iterated over and displayed on a web page. The application also includes routes for displaying all blog posts and individual blog post pages, using Twig templating engine to render the views.