QT is a cross-platform application framework.

QML is the name of the LANGUAGE (just like C++, which is ANOTHER language...)

QML stands for Qt Meta Language or Qt Modelling Language is a user INTERFACE markup language.

QtQuick is a toolkit for QML, allowing to develop graphical interface in QML language (there are other toolkits for QML, some are graphical like Sailfish Silica or BlackBerry Cascade, and some are non-graphical like QBS which is a replacement for QMake/CMake/make...)

QtQuick 1.x was Qt4.x-based and used the QPainter/QGraphicsView API to draw the scene. QtQuick 2.X was introduced with Qt5.0, based on Scene GRAPH, an OpenGLES2 abstraction layer, highly optimized.

With Qt5.1, Scene Graph was enhanced to use multithreading (QtQuick 2.1) With Qt5.2,

Qt is a cross-platform application framework.

QML is the name of the language (just like C++, which is another language...)

QML stands for Qt Meta Language or Qt Modelling Language is a user interface markup language.

QtQuick is a toolkit for QML, allowing to develop graphical interface in QML language (there are other toolkits for QML, some are graphical like Sailfish Silica or BlackBerry Cascade, and some are non-graphical like QBS which is a replacement for QMake/CMake/make...)

QtQuick 1.x was Qt4.x-based and used the QPainter/QGraphicsView API to draw the scene. QtQuick 2.X was introduced with Qt5.0, based on Scene Graph, an OpenGLES2 abstraction layer, highly optimized.

With Qt5.1, Scene Graph was enhanced to use multithreading (QtQuick 2.1) With Qt5.2,