Lua, is a script, and can run in macroquest
Macro language, is a custom script language for macroquest, it can run in macroquest
Plugins are compiled programs made in c++, and if designed for it, can run in macroquest.
Kissassist is a macro that runs using the macro language that was custom made for macroquest.
Lua scripts will need the mq2lua plugin to run, but its not something you need to pay extra for if you have redguides very vanilla version of macroqeust.