qmake is a tool to create makefiles for Qt Creator projects
qmake errors is about qmake error.
For an overview of all qmake functions, go to the page about qmake functions.
For an overview of all qmake variables (personally, I'd have called them 'qmake directives'), go to the page about qmake variables.
To view where to put qmake arguments, go to the page about qmake arguments.
For an overview of all qmake mkspecs, go to the page about qmake mkspecs.
qmake source code
The qmake source code can be downloaded from the Qt gitorious repository, in the folder '/qmake'.
qmake misc
Create a Visual Studio project file: 'qmake -tp vc myqtproject.pro'
Create a Qt .pro file from files in the folder: 'qmake -project'. Note: on a Windows computer, use the MS-DOS command prompt for this, instead of the Git Bash: the Git Bash will take its time to run out of memory and crash