A topic in DITA is an independent chunk of information covering a single idea or task, authored as a unit, and stored in its own file. Topics are categorised by information type. DITA’s topic-based architecture enables the same topic to be used in different publications.
—The DITA style guide best practices for authors.
A topic file doesn’t have any title or section marker. It is hierarchy agnostic. The main reason for this is easy reutilization. You should be able to include the same topic file under different titles or contexts. Therefore, the modular nature of DITA documentation architecture.
A topic file accepts dynamic expansion features available in Jekyll. For example, a documentation topic can receive include arguments, can include other documentation topic inside, can contain loops and conditionals to present content in clever ways.
A topic file is organized in the _includes/topics/<type> directory structure.
examples/jekyll/_includes/topics/
├── concepts
│ └── page-layout/announcement/presentation.md
└── tasks
└── page-layout/announcement/adding.md
In this directory structure, <type> can be either concepts, tasks, or references.
Concept topics are used to document conceptual or overview information. They contain background information that users must know before they can successfully work with a product or within a process. Concepts can be broken into sections, but they are primarily comprised of simple paragraphs and unordered lists.
—The DITA style guide best practices for authors.
Task topics are used to document the steps of a particular task or procedure, or to document the stages within a high level process. Task topics are the building blocks for task-oriented documentation. Task topics are more strictly structured than concept and reference topics.
—The DITA style guide best practices for authors.
Reference topics are used to describe features of sets of things, such as codes, types and commands. Information that normally demands tabular presentation probably belongs in reference topics. Catalogues, directories and bibliographies are good examples of reference topic information. Reference topics are often organised into tables.
—The DITA style guide best practices for authors.