wxWidgets is an open-source C++ library that allows developers to create cross-platform applications. It provides a set of tools and components for building graphical user interfaces (GUIs) that can run on various operating systems, including Windows, macOS, and Linux. The library is designed to be easy to use, enabling developers to write code once and deploy it across multiple platforms without significant changes. wxWidgets supports a wide range of features, including event handling, drawing graphics, and managing resources, making it a popular choice for software development.