The most notable reason they exist in the first place is VTOL or VerTOL capability, which stands for Vertical Take-Off and Landing. Although helicopters were invented in the 20th century, the idea was firstly thought out by Leonardo da Vinci in the 15th century, which he defined as 'air screw'. Helicopters ability to fly and land vertically, eliminates the need for a runway like in a winged aircraft. This particular feature enables the helicopters to hover and access many impossible areas.
Helicopters as air ambulances have greatly increased the percentage of severely injured victims that being saved because of the lifesaving equipment prepared on the helicopters and the aerial speed generated by the helicopters to get to the nearest health care facility. The universal flight capability of a helicopter makes them favorable among many military transports and emergency services. The most iconic helicopter is the Bell Huey, designated UH-1 "Iroq" which serves as the main transport aircraft during the Vietnam War in the 60's. This helicopter was the star of many popular Vietnam War themed movies such as Tour of Duty and We Were Soldiers. Apart from serving its purpose as a light assault platform, they were mainly responsible as a "Medivac" or Medical Evacuation, much like an air ambulance helicopter, except with bullets flying past (and through) them.
In much more peaceful times, helicopters can be found deployed all over the world as air ambulances. These modern 'helis' are essentially flying hospitals. Due to their nature in rescuing people from remote inhospitable areas, far away from any hospital, they must be fully equipped to give first aid treatment to those in medical need as far as the journey to the nearest facility takes. This alone escalates the operational cost of these helis. A big helicopter with such level of equipment, single rotor, twin turbofan engine producing 1500 SHP, will consume about 80 imperial gallons an hour, or about 320 liters of aviation fuel. The price of a these helicopters (typical air ambulance) with life support equipment will set you from US $ 5.000.000 upward, depending on types and level of equipment.
Man have made many engineering marvels during the last century, the helicopter is without a doubt one of the most important, especially its noble roles of saving humanity during emergency operations.