What is "qt"

Qt was created by Trolltech, passed by Nokia, and is currently developed and maintained by Digia.

The current version:

To latest official version is the 5.14. The main version (5.x) indicates the compatibility of API.

Resources:

There is an extensive official documentation (all classes) available on the project website, including tutorials and examples, which can serve as a reference for responses. Qt also provides an integrated development environment (IDE) called Qt Creator. Although created with a focus on developing Qt applications, it can be used to create regular C/C++ applications as well.

Tag recommendation:

Often you will see questions specifically marked as Qt3, Qt4 or Qt5 to indicate that the question is related to Qt 3.x, 4.x, 5.x respectively. Qt 3.x is no longer officially supported and Qt 5.x is the recommendation for new applications, so this should be assumed in the absence of version information.

Questions should also be marked with the language used: c++, qml and javascript.

Written recommendation:

Don’t confuse "Qt" with "QT" (Quicktime), which is an extensible multimedia framework developed by Apple Inc.