An electronic nose (e-nose) is an artificial olfaction system that employs an array of gas sensors combined with pattern recognition algorithms to achieve holistic perception and analysis of complex odors. Compared with other human-like sensory modalities, artificial olfaction has long lagged. Accordingly, this review constructs a comprehensive, system-level framework of electronic nose technology from a holistic perspective as follows: ① tracing the development trajectory of electronic nose technology and clarifying the characteristics and evolution of each stage; ② explaining its working principles and system architecture, highlighting the coordination among functional modules; ③ analyzing the sensing elementsthrough their response mechanisms, material properties, and structural design; ④ comparing traditional data processing and pattern recognition methods with advanced intelligent algorithms in terms of differences, applicability, and development trends; ⑤ summarizing practical deployment and challenges based on representative application cases; and ⑥ discussing frontier research directions and identifying industrial bottlenecks. E-nose technology has progressed from mechanical devices and array-based chemical sensors to commercial systems, with material nanostructuring and intelligent algorithms significantly enhancing performance. These advances have enabled applications in disease diagnosis, agriculture, public safety, and energy. Future breakthroughs will depend on coordinated innovations across sensing materials, device design, intelligent algorithms, and system architecture.This review provides a comprehensive, holistic reference for researchers and practitioners, guiding both the study and practical deployment of electronic nose systems.