More information about the Markdown output types is available in the DITA-OT documentation: https://www.dita-ot.org/dev/topics/dita2markdown.html.
The generated Markdown content can be used with a static web site generator (such as MKDocs) to build a web site: https://blog.oxygenxml.com/topics/publishing_dita_content_using_a_markdown_static_web_site_generator.html.