This chapter discusses the field of the Internet of Things, or better known as IoT, and various concepts related to it along with its vast applications and various challenges faced by IoT in the present world. A bit of the history of IoT is also given so that the readers can get a sense of how long ago the concept of IoT was conceived before becoming the revolution it is today. It goes over some of the important milestones in the history of IoT from its naming to its widespread adoption. Some of the applications of IoT, namely, in households, healthcare, industries, and renewable energies are also discussed to show the fields that have already begun to integrate IoT technologies in their operation. A brief description of the enabling technologies of IoT is also given with the purpose that the readers will be able to grasp the overall working of an IoT system. It then explores the recent developments and achievements in the field of IoT to give readers a glimpse of the present-day landscape of IoT. Finally, the chapter also touches upon the many different kinds of issues and challenges that present-day IoT systems are facing. These range from the technical aspects of IoT such as compatibility, interoperability, and security to the more ethical aspects like privacy.