Unmanned Aerial Vehicles (UAVs) have a variety of applications in our daily life that have attracted the attention of many researchers around the world. There are a variety of innovations in the flight mechanisms that UAVs are applying for flight. There is also a significant interest in the development of new types of drones that can fly autonomously in different locations, such as cities, marine, and space environments, and perform various missions. This paper reviews the different configurations, flight mechanisms, and applications of drones. First of all, UAVs are divided into four main categories, including Horizontal Takeoff and Landing (HTOL), Vertical Takeoff and Landing (VTOL), Hybrid, and Bio-Based drones. Then each category is divided into some sub-categories to have a coherent review. The characteristics, advantages, and drawbacks of each category are discussed elaborately. Moreover, a comprehensive study is carried out on the applications of UAVs and their specifications.
