Qt is a cross-platform software development framework for creating applications with graphical user interfaces (GUIs). It allows developers to write code once and deploy it across multiple platforms, including Windows, Mac OS, Linux, Android, and iOS. Qt provides a range of tools and libraries for developing applications, including API reference documentation, sample code, and a visual designer tool for creating and editing UIs. It also has support for a variety of programming languages, including C++, Python, and JavaScript. Overall, Qt is a powerful and flexible framework for building modern software applications.