User Interface: The user interface, in the industrial design field of human–machine interaction, is the space where interaction between humans and machines occurs. 

Graphical user interface: In computing,^[1] graphical user interface (GUI, sometimes pronounced 'gooey')^[2] is a type of user interface that allows users to interact with electronic devices through graphical icons and visual indicators such as secondary notation, as opposed to text-based interfaces, typed command labels or text navigation. GUIs were introduced in reaction to the perceived steep learning curve of command-line interfaces (CLI),^[3][4][4] which require commands to be typed on the keyboard.