The piezoelectric effect is a phenomenon where certain materials generate an electric charge in response to applied mechanical stress. This effect occurs in materials like quartz and certain ceramics, which can convert mechanical energy into electrical energy and vice versa. When pressure is applied to these materials, their internal structure changes, leading to a displacement of electrical charges. This property is utilized in various applications, such as in microphones, speakers, and sensors, where converting sound waves or vibrations into electrical signals is essential for functionality.