Qt (pronounced officially as cute (/kyut/) though commonly pronounced as Q.T. (/ˈkyu ti/)) is a cross-platform application development framework widely used for the development of GUI programs (where it functions like a cross-platform widget toolkit), and also used for developing non-GUI programs such as console tools and servers. wikipedia
Qt was created by Trolltech, and is currently developed and maintained by Digia.
The latest official release is 5.3.2. The major version indicates API and binary compatibility.
There is extensive official documentation (all classes) available on Qt's website, in addition to tutorials and examples. You will often see these tutorials and examples referenced in the questions and answers on this site. Qt also provides an integrated development environment named Qt Creator. Though it mainly aims at creating Qt applications, it can be used to create regular C++ applications.
You will often see questions tagged specifically as qt3, qt4, or qt5 to indicate that the question is related to Qt 3.x, 4.x, or 5.x respectively. Qt 3.x is no longer supported and Qt 5.x has been released a while ago, so the default when version information is lacking is to assume version 5.x of the API.
Qt is a cross-platform application development framework, but
QT (QuickTime) - is an extensible multimedia framework developed by Apple Inc.
Qt is available under three different licenses:
- GNU General Public License (GPL) version 3.0
- GNU Lesser General Public License (LGPL) version 2.1
- Qt Commercial License (which comes in three versions with different features and prices: "Indie Mobile", "Professional" and "Enterprise")