The contemporary mobile communication has undergone a significant shift toward a novel phase characterized by the emergence of beyond 5G (B5G) and 6G technologies. These advancements underscore a focus on enhanced spectral efficiency, minimized latency, and expansive connectivity. This paper thoroughly examines 6G wireless communication networks, including their architectural framework, key technologies, application scenarios, use cases, and challenges. The architectural blueprint of 6G networks integrates space, terrestrial, aerial, and undersea communications to facilitate deep connectivity across various scenarios, which is to meet the increasing future communication requisites. Toward this end, the paper proposes 15 key technologies such as terahertz communication, visible light communication, dynamic spectrum sharing, ultra-massive multiple-input multiple-output (MIMO), and in-band full-duplex. Furthermore, typical scenarios and emerging use cases of 6G are detailed. Conclusively, this paper expounds upon potential challenges in developing and suggests the corresponding solutions, fostering a global dialogue on this transformative technological frontier.