Ginger was used and exported by Indians some 5000 years ago. It originated in South East Asia. It was a rich and costly spice among Romans and Arabs. When Arabs travelled to Africa they planted the roots thus spreading the cultivation of it. Back in 14th century Ginger was so costly that one pound costed 1 whole live sheep.
Ground ginger is the dried grounded form of Ginger. Its basically used for stacking as spice for cooking purpose. Its more convenient to store and used many dishes like smoothies and sauces.
The method used to create ground ginger from fresh ginger reduces the amount of gingerol (one of the ingredients that contributes to its health properties) but also increases levels of other important components.