Here is a Canon RF-S 18-150mm f/3.5-6.3 IS STM review by one of our favorite…
CanonUSA on YouTube posted part 3 of the 9 parts series about Canon EF lenses, this video is about STM lenses:
Canon STM lenses have stepping motors that allow you to focus quietly and follow your subject smoothly. Photographer and educator Matt Kloskowski demonstrates the quiet smoothness of Canon’s STM technology.
See the first 2 videos here.