I feel like doing this, and I was wondering what book and other resources the Mod Gods here would recommend? Some sort of breadboard kit and a multimeter would be the way to go? (Btw - I'm in the UK, which may make a difference re. product names.)
Read, read, read. Find a nice simple project and give it a try.
MOSFETs, they're used for switches in our lights. Either high speed switching used in step up or step down regulators for LEDs. Low speed switching used when you just use a big MOSFET in place of a high current switch in a powerfull incan.
Linear regulators or Low Drop Out regulators (LDO). These are self variable resistors that adjust their resistance to maintain a constant output voltage or current.
PWM or Switched Mode Power Supplies. These are the controllers used to build step up or stepdown drivers for LEDs. Or a PWM regulator for powerful incans like the PIR.
For PWM/Switched mode supplies requires an oscilloscope.