This chapter provides a detailed overview of the sonochemical process, focusing on its core principles, mechanisms, and applications. It begins by introducing fundamental concepts of sonication, including acoustic cavitation, bubble types, sonoluminescence, and techniques for characterizing sonoactivity. The chapter then explores ultrasonic equipment design and its role in inducing chemical reactions through sound waves. Critical factors influencing sonochemical efficiency are examined, such as reactor design, driving frequency, acoustic power, and solution properties. The formation of reactive oxygen species (ROS) and reductive species (RS) in sonochemical processes is discussed, along with the degradation pathways activated by these species. Applications of sonolysis for pollutant degradation are explored, highlighting its effectiveness in removing organic pollutants and treating industrial effluents. The chapter also delves into synergistic sono-hybrid advanced oxidation processes (AOPs), including sono-Fenton, sono-ozonation, sonophotocatalysis, and sono-electrochemical processes. Furthermore, the potential of sonoprocesses for wastewater treatment is examined, with a focus on their application to industrial effluents, complex matrices, and sludge reduction. Finally, the chapter explores the challenges and emerging opportunities in the field, offering insights that facilitate a deeper understanding of the numerical simulations discussed in the subsequent chapters. This comprehensive review seamlessly integrates practical applications with the theoretical foundation of the book, paving the way for advancements in the field of sonochemistry.