ConTeXt is a TeX macro package like LaTeX and eplain. It provides a consistent, key-value driven user interface, supports all TeX engines, is tightly integrated with LuaTeX & Metapost, and supports grid-typesetting, PDF/A, PDF/X, XML/XHTML & ePub export.
ConTeXt, in the words of the ConTeXt wiki, is a document markup language and document preparation system based on TeX. It was designed with the same general-purpose aims as LaTeX of providing an easy to use interface to the high quality typesetting engine provided by TeX. However, while LaTeX insulates the writer from typographical details, ConTeXt takes a complementary approach by providing structured interfaces for handling typography, including extensive support for colors, backgrounds, hyperlinks, presentations, figure-text integration, and conditional compilation. It gives the user extensive control over formatting while making it easy to create new layouts and styles without learning the TeX macro language. ConTeXt’s unified design avoids the package clashes that can happen with LaTeX.
ConTeXt provides a multi-lingual user interface with support for markup in English, Dutch, German, French, and Italian and support for output in many languages including western European languages, eastern European languages, Arabic, Chinese, Japanese, and Korean. It also allows the user to use different TeX engines like pdfTeX, XeTeX, and LuaTeX without changing the user interface.
ConTeXt integrates a superset of MetaPost called MetaFun which allows the users to use the drawing abilities of MetaPost for page backgrounds and ornaments. Metafun can also be used with stand alone with MetaPost.
ConTeXt also provides a macro package for typesetting chemical structure diagrams with TeX called PPCHTeX. This package can also be used with plain TeX and LaTeX.
Use of tags
Getting started with Context
Hans Hagen's ConTeXt: An excursion provides a good, very readable introduction to the basics of document preparation in ConTeXt, although it really targets Mk. II. Taco Hoekwater has authored the current User Manual which, besides being the authorative reference for current functionality, also provides excellent summaries of such issues as how to handle fonts in typesetting. Hans Hagen's METAFUN: Context mk iv describes the Metapost-based approach to layout in Context.