Head-mounted displays (HMDs) are a type of wearable technology that typically consists of a headset or pair of goggles with a small screen or projection system that covers the user's eyes. HMDs can be used for a variety of purposes, including virtual reality (VR), augmented reality (AR), and mixed reality (MR) applications. In VR, HMDs can completely immerse the user in a virtual environment, allowing them to interact with and explore a computer-generated world. AR HMDs overlay digital information onto the user's view of the real world, enhancing their perception and interaction with their surroundings. MR HMDs combine elements of both VR and AR, allowing users to interact with both virtual and physical objects in a mixed reality environment. HMDs have a wide range of applications, including gaming, training and simulation, medical imaging, engineering design, and more. They have the potential to revolutionize how we interact with and experience digital content, offering a more immersive and interactive experience than traditional display technologies.