Hydraulic fracturing, or fracking, is a drilling process in which an L-shaped shaft is bored first vertically, then horizontally, through shale deposits several thousand feet below the surface.
The process gets its name from what happens next: Once drilling is complete, the shaft is punctured so that a mixture of water, chemicals and sand can be forced -- under extreme pressure -- into the surrounding shale.
The shale fractures, releasing hydrocarbons such as oil and natural gas that are trapped inside. Once drilling is complete, the well is capped and tied into nearby pipelines, allowing the hydrocarbons to be captured and used.
Hydraulic fracturing is not new. Drilling companies have fractured shale for decades to release and extract trapped hydrocarbons nearby. What has changed, however, is the scale of the energy available due to advances in horizontal drilling.
Instead of one well extracting oil and natural gas in a small area around a vertical shaft, horizontal drilling allows a single well to draw hydrocarbons from a much larger region of underground shale.
As a result, according to the U.S. Census Bureau, the oil and natural gas extraction sector of the national economy grew a staggering 24 percent between 2007 and 2012.
Fracking's effects on the environment remain an open and hotly debated question. In some regions, fracking is believed to have altered the chemistry of groundwater as hydrocarbons leach into underground aquifers. It also has been blamed for small earthquakes in what had been geologically quiet areas such as Youngstown, Ohio.
Despite such concerns, fracking's economic impact is staggering.