Changes

Mark IV is the name of the [[LuaTeX]]-aware part of ConTeXt; that is, when you use ConTeXt over the LuaTeX engine instead of PDFTeX or XeTeX. You run it with

It takes advantage of the amazing capabilities of LuaTeX and opens up a whole new world of possibilities, in particular with fonts.

In the distribution the MkII files have suffix 'mkiv'. There are also files with suffix 'mkvi' and more will follow. The most significant difference is that these files use a different (and still somewhat experimental) syntax.