In a nutshell, Livemark is just a text processor. It takes a Markdown document and outputs an HTML document. It is also possible to output different formats but the main Livemark specialization is Markdown-to-HTML conversion.
Livemark's core only provides an abstract classe like Project, Document, or Snippet. The actual work is done by various plugins like HtmlPlugin, SitePlugin, or TablePlugin. You can find their description in the Livemark Markdown and Livemark Features sections.
On the figure below we present Livemark's building flow schematically: a Markdown document containing various snippets being converted to an HTML document containing various markup blocks by Livemark and its plugins: