This paper reviews the advancements in piezoelectric energy harvesting from mechanical vibrations, focusing on the development of simple and efficient energy harvesting devices. The authors highlight the importance of piezoelectric materials, which can convert mechanical vibrations into electrical energy with high efficiency. Key topics include the classification of piezoelectric materials into piezoceramics and piezopolymers, their respective characteristics, and the mathematical modeling of vibrational energy harvestings. The paper also discusses the direct and converse piezoelectric effects, providing detailed constitutive equations for these phenomena. Additionally, it reviews various types of vibration devices and the performance of piezoelectric energy harvesting systems, emphasizing the potential of piezoelectric materials as a self-power source for portable electronics and wireless sensor networks.This paper reviews the advancements in piezoelectric energy harvesting from mechanical vibrations, focusing on the development of simple and efficient energy harvesting devices. The authors highlight the importance of piezoelectric materials, which can convert mechanical vibrations into electrical energy with high efficiency. Key topics include the classification of piezoelectric materials into piezoceramics and piezopolymers, their respective characteristics, and the mathematical modeling of vibrational energy harvestings. The paper also discusses the direct and converse piezoelectric effects, providing detailed constitutive equations for these phenomena. Additionally, it reviews various types of vibration devices and the performance of piezoelectric energy harvesting systems, emphasizing the potential of piezoelectric materials as a self-power source for portable electronics and wireless sensor networks.