Fracking is short for fracturing specifically fracturing rock to release natural gas trapped in it. Water and chemicals under pressure are used to do the work both of which end up in ground water and soil.

The US govmint under Bush and Co gave oil and gas companies amnesty from environmental laws. So these companies have been buying up mineral rights anywhere there are deposits of trapped gas in a particular type of rock (some kinda shale).

According to the map shown in the film trailer the practice is quite prevalent in southeast England too.