If your software only supports a terminal or command-line-based interface, your target audience is likely limited to only people who know how to use the command line. Providing a Graphical User Interface (GUI) for your software widens your target audience and gives users a friendly and intuitive interface so that they can use the software effortlessly. For building GUIs, most languages provide frameworks that consist of several native libraries that are composed together and can access the graphics and the I/O interfaces of the platform. This enables developers to easily build GUIs for their applications without worrying about the low-level details.
There are quite a few popular GUI frameworks targeting desktop platforms such as Qt, GTK+, and ImGUI, which are available for mainstream languages. At the time of writing this book, Rust doesn...