The paper defines a multirotor unmanned aerial vehicles and all knowledge about them. In this paper is presented a historical development of unmanned aerial vehicles and multirotor aircraft, which has led to today's multirotor unmanned aircraft that is used today in civil sector since they were exclusively designed for military use. Paper explains the basic parameters and laws of kinematics, physics and control of tetra copter (multi-rotary four-rotor aircraft) and the basic components such an aircraft consists, starting from the construction, the propulsion system, management system to the control system. Since the aircraft have entered in civil use, it is a day of the possible areas and sectors in which these aircraft are used daily, and is a summary of the legal regulations which are regulating this area in the Republic of Croatia. The aim of the paper is to give a general cross-section of comprehension and knowledge of this type of aircraft. The result of the work is a complete overview of general information on unmanned aerial vehicles, its parts and modes and the possible areas of application of the aircraft.