Fracking is fracturing rock by pressurized liquid
Fracking, or hydraulic fracturing, is forcing fractures in a rock layer, by fluid that is put under pressure. It can happen naturally, but it is now used to force oil and natural gas from shale.
Proponents of hydraulic fracturing point to the economic benefits from the vast amounts of previously out of reach hydrocarbons. Opponents point to potential environmental effects, such as contamination of ground water, risks to air quality, the migration of gases and hydraulic fracturing chemicals to the surface, surface contamination from spills and flowback and the health effects of these. For these reasons hydraulic fracturing has come under scrutiny, with some countries suspending or banning it.
However, some of those countries, including most notably the United Kingdom,[8] have recently lifted their bans. Now they have regulations instead of outright prohibition. It turns out that the UK has huge gas reserves if fracking is used.
Source: Wikipedia