Concepts
Doc
One Markdown document.
Docset
A set of Docs, e.g. from folders or .zip files of .md files, optionally filtered to a subset of those Docs and a subset of content within those Docs.
Section
A subset of a Doc that contains a Heading followed by the content associated with it (including subsections).
Syntax tree
a.k.a. "AST", — this is a tree of Elements that code gets parsed to.
Element
For Markdown code, syntax tree elements include Link, CodeBlock, etc.
Post
You can consider some Docs or Sections to be "Post"s. This concept is relevant only for some post-related plugins, e.g. rss, signatures, etc.