To address the difference surrounding Qt Quick vs QML we must appreciate the fact that this is one of those things that come once in a while where the passive developer doesn’t have enough discernment to realize that Qt Quick and QML are not the same things.
Qt Quick was launched back in 2010 with Qt 4.7 back when Nokia owned The Qt Framework. Its motivation was the growth of mobile devices and modern user interfaces. QML naturally came into the picture around 2009 but came into significant prominence with Qt 5.0.
Explaining Qt Quick vs QML
Qt Quick is a software application framework that is part of the wider Qt framework. It is used to build custom, highly dynamic graphical user interfaces with fluid transitions and visual effects.
The Qt Quick framework contains controls and GUI elements that can be used in your application.
QML, also known as Qt Modeling Language or Qt Meta Language, on the other hand, is the user interface markup language. It is a declarative language similar to CSS and JSON used for designing user interface-based applications.
Qt Quick and QML applications can also run in a web browser through Qt for WebAssembly. There you see when trying to compare Qt Quick vs QML, it truly is an apple to oranges comparison.