The Internet of Things (IoT) is an emerging concept that extends the Internet and Web into the physical world through the widespread deployment of spatially distributed devices with embedded identification, sensing, and/or actuation capabilities. The IoT envisions a future where digital and physical entities can be linked through appropriate information and communication technologies to enable new applications and services. This survey presents a comprehensive overview of IoT technologies, applications, and research challenges. The IoT is characterized by three main pillars: identification, communication, and interaction. Smart objects, or "things," are entities that can be identified, communicate, and interact. These objects are expected to be highly heterogeneous in terms of capabilities and will require scalable, secure, and energy-efficient solutions. The IoT will also require ubiquitous data exchange through proximity wireless technologies, energy-optimized solutions, and localization and tracking capabilities. Research challenges in the IoT include the development of appropriate means for identifying smart objects and enabling interactions with the environment. Key building blocks for IoT include wireless sensor networking technologies and RFID. The IoT also shares characteristics with ambient intelligence, requiring distributed intelligence and self-organization capabilities. Additionally, the IoT will require distributed systems technology to enable the easy implementation of services on top of a distributed platform. Security is a critical component for the widespread adoption of IoT technologies. The three key issues requiring innovative approaches are data confidentiality, privacy, and trust. The survey also discusses the potential application fields and impact areas of IoT, as well as ongoing initiatives in the IoT space. Overall, the IoT presents a wide range of opportunities for users, manufacturers, and companies, with the potential to transform various sectors including environmental monitoring, healthcare, inventory management, and security.The Internet of Things (IoT) is an emerging concept that extends the Internet and Web into the physical world through the widespread deployment of spatially distributed devices with embedded identification, sensing, and/or actuation capabilities. The IoT envisions a future where digital and physical entities can be linked through appropriate information and communication technologies to enable new applications and services. This survey presents a comprehensive overview of IoT technologies, applications, and research challenges. The IoT is characterized by three main pillars: identification, communication, and interaction. Smart objects, or "things," are entities that can be identified, communicate, and interact. These objects are expected to be highly heterogeneous in terms of capabilities and will require scalable, secure, and energy-efficient solutions. The IoT will also require ubiquitous data exchange through proximity wireless technologies, energy-optimized solutions, and localization and tracking capabilities. Research challenges in the IoT include the development of appropriate means for identifying smart objects and enabling interactions with the environment. Key building blocks for IoT include wireless sensor networking technologies and RFID. The IoT also shares characteristics with ambient intelligence, requiring distributed intelligence and self-organization capabilities. Additionally, the IoT will require distributed systems technology to enable the easy implementation of services on top of a distributed platform. Security is a critical component for the widespread adoption of IoT technologies. The three key issues requiring innovative approaches are data confidentiality, privacy, and trust. The survey also discusses the potential application fields and impact areas of IoT, as well as ongoing initiatives in the IoT space. Overall, the IoT presents a wide range of opportunities for users, manufacturers, and companies, with the potential to transform various sectors including environmental monitoring, healthcare, inventory management, and security.