Qt is a free and open-source widget toolkit for creating graphical user interfaces as well as cross-platform applications that run on various software and hardware platforms. It is developed by The Qt Company and is widely used by developers to build desktop, mobile, embedded, and web applications. Qt provides a comprehensive set of tools and APIs for designing, developing, and deploying applications with a native look and feel. It includes features such as GUI components, layout management, event handling, graphics rendering, multimedia support, and platform abstraction. Qt's cross-platform capabilities allow developers to write code once and deploy it on multiple platforms without modification, saving time and effort. Qt is used by thousands of companies worldwide, including Autodesk, LG Electronics, Siemens, and Volkswagen, to build high-quality software applications for a wide range of industries and use cases.