The need to take-off and land in stringent battlefield conditions necessitates the need for Vertical Take-Off and Landing (VTOL) capabilities in Unmanned Aerial Vehicles (UAV). Also, a major issue associated with UAVs is that these aircrafts are not suitable for operations in limited airspace. This problem becomes huge especially in urban areas where the usage of runway is not possible, and UAVs usually have to fly at a relatively low speed and altitude. VTOL UAVs require less investment in infrastructure and geographical area for their operations as compared to other traditional aircrafts. Development of VTOL technology would not only strengthen our military but also eliminate the requirement of big airstrips. This paper focuses on the introduction, classification, applications and basic design process of VTOL UAVs keeping in mind the military requirements.