Hydraulic fracking is propagation of fractures through layers of rock using pressurized fracturing fluid.

Hydraulic fracking is propagation of fractures through layers of rock using pressurized fracturing fluid. This technique is primarily used in the extraction of resources from low permeability reservoirs such as shale gas, tight gas, and unconventional liquids; which are difficult to recover through regular drilling procedures.
In this process fracturing fluid is used. It consists of water, proppant, chemical additives, and guar gum. Proppant is the most integral constituent of the fracturing fluid after water. Proppant material keeps the generated fractures propped open and helps continued oil and gas recovery.