A Graphical User Interface is a man-machine interface device, in which objects to handle are drawn as icons on the screen, so the user can send controls by by a pointing device, usually a mouse or a keyboard.
It is always easy and require less skills to operate a device from a visual representations of the workspace (GUI) by simply clicking a mouse or using a keyboard rather than a command line.
The GUI can also be used to interface with other external devices located in different places.
There are a lot of different kinds of software which can be used to design a GUI platform, the choice will usually depend on personal preferences, software capabilities and the operating systems (Windows, Linux, Mac...).
Among the popular ones we have Microsoft Visual studio with its popular programming languages visual basic and C#, Labview, Python, Matlab etc.