The article presents a comprehensive survey of the sixth generation (6G) mobile communication system, aiming to provide a clear picture of its drivers, use cases, usage scenarios, requirements, key performance indicators (KPIs), architecture, and enabling technologies. It begins by addressing the question of whether 6G is necessary, highlighting the explosive growth of mobile traffic and potential use cases. The technical requirements of 6G are discussed in comparison to 5G, with a focus on KPIs. The article summarizes current research efforts and activities from leading institutions and countries, projecting a roadmap for definition, specification, standardization, and regulation. It identifies twelve potential technologies, explaining their principles, advantages, challenges, and open research issues. The conclusion outlines a vision of what 6G may look like, emphasizing its role in supporting future communication needs. The article discusses the key drivers for 6G, including the explosive growth of mobile traffic, disruptive use cases, and novel usage scenarios. It highlights the need for 6G to support a wide range of services, from traditional mobile broadband to Industry 4.0, virtual reality, IoT, and autonomous driving. The article also explores potential use cases such as holographic-type communications, extended reality, tactile internet, multi-sense experience, and pervasive intelligence. It proposes three new usage scenarios for 6G: ubiquitous mobile broadband (uMBB), ultra-reliable low-latency broadband communication (ULBC), and massive ultra-reliable low-latency communication (mULC), which are designed to meet the requirements of these use cases. The article outlines the technical requirements for 6G, including extreme capacity, reliability, efficiency, and other KPIs. It discusses the performance requirements for 6G, such as peak data rate, user-experienced data rate, latency, mobility, connection density, energy efficiency, peak spectral efficiency, and area traffic capacity. The article also highlights the importance of new technologies such as THz communications, AI, blockchain, and distributed computing in enabling 6G. It concludes by envisioning a future where 6G will be a radio-optical system, a connected intelligent platform, an integrated space-aerial-terrestrial network, and a smart compute-connect entity, transforming the whole Earth into a huge brain to support an informationized and intelligentized society by 2030.The article presents a comprehensive survey of the sixth generation (6G) mobile communication system, aiming to provide a clear picture of its drivers, use cases, usage scenarios, requirements, key performance indicators (KPIs), architecture, and enabling technologies. It begins by addressing the question of whether 6G is necessary, highlighting the explosive growth of mobile traffic and potential use cases. The technical requirements of 6G are discussed in comparison to 5G, with a focus on KPIs. The article summarizes current research efforts and activities from leading institutions and countries, projecting a roadmap for definition, specification, standardization, and regulation. It identifies twelve potential technologies, explaining their principles, advantages, challenges, and open research issues. The conclusion outlines a vision of what 6G may look like, emphasizing its role in supporting future communication needs. The article discusses the key drivers for 6G, including the explosive growth of mobile traffic, disruptive use cases, and novel usage scenarios. It highlights the need for 6G to support a wide range of services, from traditional mobile broadband to Industry 4.0, virtual reality, IoT, and autonomous driving. The article also explores potential use cases such as holographic-type communications, extended reality, tactile internet, multi-sense experience, and pervasive intelligence. It proposes three new usage scenarios for 6G: ubiquitous mobile broadband (uMBB), ultra-reliable low-latency broadband communication (ULBC), and massive ultra-reliable low-latency communication (mULC), which are designed to meet the requirements of these use cases. The article outlines the technical requirements for 6G, including extreme capacity, reliability, efficiency, and other KPIs. It discusses the performance requirements for 6G, such as peak data rate, user-experienced data rate, latency, mobility, connection density, energy efficiency, peak spectral efficiency, and area traffic capacity. The article also highlights the importance of new technologies such as THz communications, AI, blockchain, and distributed computing in enabling 6G. It concludes by envisioning a future where 6G will be a radio-optical system, a connected intelligent platform, an integrated space-aerial-terrestrial network, and a smart compute-connect entity, transforming the whole Earth into a huge brain to support an informationized and intelligentized society by 2030.