This chapter presents a systematic exploration of single object tracking (SOT), focusing on its core definitions, challenges, and the evolution of its tasks. SOT is defined by three key attributes: temporal continuity, category agnosticism, and instance discrimination, which enable machines to emulate human dynamic visual abilities. The chapter categorizes SOT tasks into short-term tracking (STT), long-term tracking (LTT), and global instance tracking (GIT), highlighting their increasing complexity in addressing real-world challenges such as occlusion, lighting variations, and fast motion. By analyzing these tasks and their associated challenges, the chapter emphasizes the need for adaptive algorithms and robust evaluation frameworks to drive innovation in the field. This foundation aims to guide future research toward developing resilient, intelligent tracking systems for diverse applications.