Horizontal drilling, also known as directional drilling. The concept was developed in 1920 and has long since been redesigned to achieve better drilling also creating a smaller footprint. It is called horizontal drilling because it allows oil workers to drill in many different directions including horizontally.
Directional drilling allows multiple wells to be dug from the original vertical source which saves time, resources and is much more environmentally friendly. Also, drilling at an angle other than vertical can obtain information, such as the location of the wells, therefore multiple holes do not need to be dug up.
Horizontal drilling has been known to increase productivity by 20 times more than vertical drilling. Horizontal drilling is expensive. When combined with hydraulic fracturing, a well can cost up to three times as much per foot as drilling a vertical well. The extra cost is usually recovered by increased production from the well.
According to Wikipedia, Hydraulic fracturing is highly controversial in many countries. Its proponents advocate the economic benefits of more extensively accessible hydrocarbons. Opponents argue that these are outweighed by the potential environmental impacts, which include risks of ground and surface water contamination, air and noise pollution, and the triggering of earthquakes, along with the consequential hazards to public health and the environment.