I will be talking about the UAV(unmanned aerial vehicle) for this post. A UAV is an aircraft that flies without a human crew on board. The UAV is defined as a reusable, uncrewed vehicle capable of controlled, sustained, level flight and powered by a jet or reciprocating engine to distinguish it from missles. The earliest UAV was the "Aerial Target" developed by Archibald Low. It then advanced rapidly during the second world war.
However, these were mostly used for target practice and the first modern UAV was developed by Israel and used in the Yom Kippur war against Lebanon.
There are many applications of the UAV, though the most common applications are reconnaissance and combat.
A very commonly known UAV is the Predator drone. It has many advanced sensors and is fitted with missiles for combat. This drone has been used on countless missions by the USA and has succeeded many times. The main reason why the US use UAVs is that it is controlled miles away from the area that it is used, thus no one dies when the drone is shot down, as compared to an actual airplane.