This report provides a comprehensive overview of multi-rotor drones, also known as multi-rotor UAVs, exploring their diverse applications, security concerns, and underlying technologies. The introduction defines UAVs and highlights their evolution from military applications to widespread civilian use, emphasizing the cost-effectiveness and flexibility of multi-rotor units. The report details various types of multi-rotors, including bi-copters, tri-copters, quadcopters, penta-copters, hexa-copters, and octa-copters, outlining their features and capabilities. It then delves into specific applications across sectors like agriculture (crop monitoring, irrigation, disease detection, soil mapping), delivery of goods (healthcare, transportation), fisheries, forestry, wildlife protection, defense, civil applications, search and rescue, remote sensing, and infrastructure inspection. The report also addresses security issues and challenges posed by drones, drone biometrics, pilot identification, and the integration of machine learning techniques. Furthermore, it examines the architecture and components of drones, including their functions, and concludes with an overview of the challenges facing the drone industry.