These are helicopters built for combat. Some are used in non-combat roles as well. Many of them have evolved beyond the supportive and limited roles of the 21st century, and into realms previously unheard of.
For example, the AC120 and Boomslang are used in the same roles as fighter aircraft and even fight directly alongside them. Some attack helicopters are even capable of supersonic flight, something which was impossible in the 21st century.