ConTeXt is a macro package created by Hans Hagen of Pragma ADE (which stands for Advanced Document Engineering); it started as a production tool for Pragma (which is a publishing company). ConTeXt is a document-production system based, like LaTeX, on the TeX typesetting system. Whereas 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 also integrates MetaFun, a superset of MetaPost and a powerful system for vector graphics. MetaFun can be used as a stand-alone system to produce figures, but its strength lies in enhancing ConTeXt documents with accurate graphic elements.
The development of LuaTeX was originally driven
by ConTeXt, almost from the start of its project. Nowadays,
ConTeXt it is distributed in two versions - mark two (files with
mkii) which runs on pdfTeX but is not under
active development, and mark four (files with extension
mkiv) (which runs on LuaTeX and is where development
ConTeXt has a large developer community (though possibly not as large as that of LaTeX), but those developers who are active seem to have prodigious energy. Support is available via the ConTeXt Garden and via the mailing list. A “standalone” distribution (a TeX distribution with no macros other than ConTeXt-based ones) is available as "ConTeXt Standalone" (also known as “ConTeXt Minimals” or the “ConTeXt Suite”) - it provides a ConTeXt system on any of a number of platforms, executing either Mark II or Mark IV ConTeXt.
Note that CTAN does not hold the primary distribution of ConTeXt - potential users should refer to the ConTeXt Garden for details of the current distribution.