Take a look at the 'inside scoop' of a small 6-speed manual geared transmission. Of course, not all transmissions are built exactly the same, but this one is from a lawn mower, making it fairly simple and easy to investigate.
If you haven't seen my other transmission videos, I encourage you to especially check out the Hydrostatic Transmission, since it's the coolest (
https://youtu.be/h3K_THDapTM)!
Any questions, ask away!