DocBook is a semantic markup language. That is, it specifies the meaning of the elements in a document, not how they are intended to be presented to the end user. It provides separation between the content of the document and the visual representation. While DocBook is a readable markup language, it is not intended to be read by end-users in its DocBook form.
The purpose of DocBook XSL is to provide a standard set of transformations from DocBook to several presentational formats.
DocBook XSL provides for transforms into the following formats:
DocBook XSL also has transformations to slide-like formats for HTML and XSL-FO.
DocBook XSL's stylesheets are highly configurable. Each of the different formats has a number of XSLT parameters available for simple customization. For example, the XSL-FO transforms allow the user to define the size of the pages. Additionally, the XSLT documents themselves are modular; it is possible for the user to add, change, or replace particular levels of functionality. This can allow DocBook XSL to process new documentation tags added to the standard DocBook, or to simply change how the XSLT's generate the resulting format.