Recommended · for beginners
Transistor / MOSFET tutorial
Why people recommend it
A beginner tutorial on using BJTs and MOSFETs as switches, often suggested when a microcontroller pin needs to drive a motor, laser or other larger load.
Watch for: the flyback diode across the motor at 4:03
In their words
For transistors, there's a simple tutorial here that I like.
AndrejaKo on electronics.stackexchange.com, Nov 2011. CC BY-SA.