Unconventional shale gas is especially common right now and the development of unconventional gas has been a frequent topic of discussion lately. They are normally related to ultra-low permeabilities and have to be developed with extra processes like fracturing or multistage fracturing. Over the past decades, the oil and gas sector has developed high level technologies, including stimulation technologies, to explore oil and gas. Since the shale formation has very special characteristics, the fracturing processes are somehow different from traditional fracturing technologies in the oil and gas sector. The oil and gas expertise should be transferred to the shale gas production. In order to better understand the most important yet complex process in developing shale gas, this paper is going to provide an overview of the basic knowledge of oil and gas fracturing with explanations of the important characteristics of fracturing processes and then the focus will be on the explanation of horizontal wells fracturing for shale gas production. The following questions will be discussed throughout the paper: What do fracturing fluids contain? What kind of fracturing processes do exist? What is refracturing? How does multistage fracturing work? How can we evaluate the environmental issues?