This paper provides a comprehensive survey of research on egocentric vision understanding, which has been attracting attention due to advances in AI and wearable devices. Egocentric vision, which collects visual and multimodal data through body-worn cameras or sensors, offers a unique perspective for simulating the human visual experience. This paper systematically analyzes the components of egocentric scenes, categorizing tasks into four major areas—subject understanding, object understanding, environment understanding, and mixed understanding—and delves into the subtasks within each category. Furthermore, it summarizes key challenges and trends in this field and provides an overview of high-quality egocentric vision datasets, providing valuable resources for future research. By summarizing recent advances, it anticipates widespread applications of egocentric vision technology in fields such as augmented reality, virtual reality, and embodied intelligence, and suggests future research directions based on these latest developments.