The Internet of Things (IoT) is a recent revolution of the Internet which is increasingly adopted with great success in business, industry, healthcare, economic, and other sectors of modern information society. In particular, IoT supported by artificial intelligence enhances considerably the success in a large repertory of every-day applications with dominant one's enterprise, transportation, robotics, industrial, and automation systems applications. Our aim in this article is to provide a global discussion of the main issues concerning the synergy of IoT and AI, including currently running and potential applications of great value for the society. Starting with an overview of the IoT and AI fields, the article describes what is meant by the concept of 'IoT-AI synergy', illustrates the factors that drive the development of 'IoT enabled by AI', and summarizes the concepts of 'Industrial IoT' (IIoT), 'Internet of Robotic Things' (IoRT), and 'Industrial Automation IoT (IAIoT). Then, a number of case studies are outlined, and, finally, some IoT/AI-aided robotics and industrial automation applications are presented.