HUD
[pronounced: huhd]
1. Heads-Up Display - a display that presents data without requiring users to look away from their usual viewpoints. The origin of the name stems from the pilots being able to view information with heads “up” and looking forward, instead of angled down looking at lower instruments.
GUI
[pronounced: goo-ee]
1. Graphical User Interface - a type of user interface that allows users to interact with programs through manipulation of graphical elements as opposed to text-based interfaces.