As a pivotal technology for extracting unconventional hydrocarbon, hydraulic fracturing stimulation alters the native balance between aqueous phases, mineral matrices, gaseous components, and microbial communities in deep geological systems, fostering a novel ecosystem that drives multifaceted geochemical processes. These processes not only lead to significant deterioration in the quality of fracturing flowback fluid but also cause reservoir damage, thereby impacting oil and gas production. Hydraulic fracturing activities implicate a broad range of critical issues spanning geology, hydrogeology, geochemistry, and environmental science. This chapter provides an overview of hydraulic fracturing and introduces foundational concepts such as unconventional hydrocarbon, hydraulic fracturing steps, fracturing fluids and additives, water–rock interactions, and engineering and environmental challenges associated with hydraulic fracturing. This chapter delineates the book’s aims and thematic boundaries while elucidating its organizational framework, equipping readers with foundational knowledge to navigate the detailed discussions in later sections.