What is DITA (Darwin Information Typing Architecture)?

DITA - Darwin Information Typing Architecture is an open standard defined and maintained by the OASIS DITA Technical Committee. The latest (current) version is 1.3, approved in December 2015. An errata document for DITA 1.3 was approved in October 2016.

DITA is an XML standard for authoring, publishing, and producing technical documents. It consists of a set of design principles that help to create and manage content separately from formatting. If you want to understand how it works, you must understand how DITA uses topics, maps, and output formats.

DITA helps to:

standardize and organize the content into topics;
make the content more versatile and portable by separating information from its format;
transform the content into other formats.

You create your content in DITA topics, apply DITA maps to define which topics move into which deliverables, then handle those maps to DITA output formats to produce your final deliverables.

Localization

DITA provides support for translation via the localization attribute group. Element attributes can be set to indicate whether the content of the element should be translated. The language of the element content can be specified, as can the writing direction, the index filtering, and some terms that are injected when publishing to the final format. A DITA project can be converted to an XLIFF file and back into its original maps and topics, using the DITA-XLIFF Roundtrip Tool for DITA-OT and computer-assisted translation (CAT) tools designed to implement the translation workflow suggested by the article "Using XLIFF to Translate DITA Projects" published by the DITA Adoption TC at OASIS.

DITA, HTML, and XML differ from each other in multiple respects.

Both HTML and DITA use tags and attributes within the tags, but whereas HTML may still work when you forget to add a closing tag, DITA and XML are very strict about their closing tags.
HTML uses a set of pre-defined tags (body, p, span, etc.), which you cannot change. However, XML, in addition to standard tags you can also use user-defined tags, which are defined in a separate file.
HTML is lenient about the order in which different tags appear in a file, but DITA is very particular about the tags that should come first and the order of the tags that should follow.
The outermost, root tag in an HTML file is html, while the root tags in a DITA file depend on the type of topic you are creating. For example, concept, task, or reference etc.

Free tools can be used for DITA, but there is a wealth of feature-rich software available on the market to make life easier for content developers.

Read more on DITA in the ClickHelp as a DITA Alternative blog post.