FSB = Front Side Bus, layman's definition would be the speed at which the CPU and RAM communicate with each other via the motherboard.
AGP Bus: No real need to learn about this, it's just there really. It's a dying breed, only found on some older system or very low end motherboards.
AMD Chips: The Intel microarchitecture is different from AMD's, therefore the chips handle data differently, if you head over to the CPUs and overclocking section and make a thread, you'll likely run into Idontcare, who knows pretty much all you'll ever need to know about CPUs and their microarchitectures. Or you could just PM him, whichever suits you. This is far from common knowledge, the info behind this is best suited to electrical engineers.
Voltage: Easiest way to define voltage would be, electrical pressure, like water pressure builds up in a pipe, electrical pressure or voltage can be built up in a circuit to generate a stronger current since it powers over the circuit's resistance to electrical flow.
Increased voltage = more current flow = more heat generated. Metals aren't perfect conductors and therefore waste power generating heat, if you had a cpu and motherboard made out of super-conductors, the closest to 0 resistance humans can create at the moment, then there'd be almost no heat generated, regardless of the voltage/current flow. Heat = enemy of all things electrical, heat causes wear and tear on components and therefore the components need adequate cooling to last longer. The cooler it is, ideally the longer it lasts assuming there are no mechanical or chemical parts on the object. (mechanical as in moving)
Wireless types: It's more of a tech difference, over time better and better routers were developed using different technologies, and were given different names over times assigned via the letters you mentioned. G and N are the most common nowadays.
SCSI: This is only important to RAID configurations if I'm not mistaken.
I suppose you have a valid point on the book, still seems a waste to me though I prefer to just get by on the knowledge I have, wait till theres something I don't know and then when I learn about it, get more involved and learn about related tech. Worked well for me so far, also a basic understanding of electricity and circuits explains a great deal to you when you look at all this hardware we discuss, maybe look into that for starters?