What are the differences between the Canon 50mm 1.8 II and STM lenses?

The main differences between the Canon 50mm 1.8 II and STM lenses are in their autofocus systems. The 50mm 1.8 II has a traditional autofocus motor, while the STM lens has a newer and quieter Stepping Motor (STM) for smoother and quieter focusing during video recording. Additionally, the STM lens may offer slightly better image quality and faster focusing speed compared to the 50mm 1.8 II.