I'll take up the challenge:

Fridge - well, the standard compressor powered refrigeration system is essentially a heat moving system. What we are doing is moving heat from the inside of the system (which is insulated and mostly "isolated" from the outside of the system) to the outside of the system. This is why you can't cool your house by opening your refrigerator's door, because the heat from the inside of the fridge is moved to the "outside" (the room it is in) - eventually, it would reach equilibrium (and the compressor would probably be overheated). So anyhow, how does this work?

Well - basically by compression and expansion.

A working fluid (the refrigerant - usually a gas in the low-pressure state, and a fluid in the high pressure state) is compressed using a compressor. This turns the gas into its fluid state, and also heats up the gas. It is moved (via the compressor) thru coils on the inside (insulated) of the system, where it is allowed to expand.

Note that in this system there is also a series of check valves and such to prevent the fluid and gas from "moving backwards" in the system; there are also stages where the gas and fluid exist at the same time (like a fizzy drink if you could see it).

During this expansion, it absorbs heat and it also gains volume (turns from a fluid back into a gas). It continues to move (with it's heat content) from the insulated side of the system (inside) to the outside of the system, where it goes thru other coils (radiator), usually with a fan or other cooling system blowing over them to remove the excess heat from them, before the gas goes back to the compressor to be compressed and turned into a fluid again - to begin the cycle anew.

That's the basics of how a refrigerator work. Now - usually, if there's a freezer section, the freezer is where the heat exchange really happens, and cold air from the freezer is periodically circulated from the freezer to the refrigerator portion to keep that side at a cooler temperature.

Air conditioners work the same way - except the "inside" is the house and the outside is...the outdoors. Heat pumps can run in reverse, so to warm your house, heat is moved from the "outside" to the inside of the house, by the very same process (even when it is "freezing" outside - there is still a ton of heat energy available).

This cycle can also be done with heat alone, provided you have a working fluid (refrigerant) which is liquid at the "outside" temperature (under whatever pressure the liquid is at); add a check valve, heat the liquid up, it will expand and turn into a gas, feed it into the insulated part of the system to absorb more heat and then into some outside coils to be cooled down and turned back into a liquid. You can make a fridge where the refrigerant is gasoline (petrol) if you so wanted to. Ammonia is another alternative. LPG can also be used like this, too.

That's basically how a propane or solar powered refrigerator works (I won't go into how dark-sky refrigeration works, suffice to say it is another form of "solar" refrigeration, more of a "backwards" method).

Car? Well - a four-cycle engine is basically this: suck (intake), squeeze (compression), bang (ignition/power), blow (exhaust). Also, for an engine to run, you need fuel, spark, and air - miss any of those (or wrong timing or proportions) things won't work. I won't go into further detail - I really could, I'm sure you can see.

Suffice to say - I could also describe that bicycle very exactly, how it works, how it is steered (the whole "turn in the opposite direction of the lean" thing...), etc.

I've got a ton of this crap shoved into my head; I relish learning new stuff all the time, no matter what it is. Sometimes (most of the time) I don't absorb it all in one shot. But I usually retain enough of it to be able to understand more a second and third time around. Some things I will probably never fully understand (higher math is my bane, though I try - also, I'll probably never understand chemistry or biology on anything more than a superficial level), but that doesn't keep them from my interest.

Why am I like this? Not sure, I've always been a very curious and inquisitive person since I was a child. I've found that having these tidbits and more of knowledge and such socked away has helped me make connections and analogies in other areas, to solve problems - and sometimes raise other questions, which just leads me down another rabbit hole at times.

As you can tell - take me to a library and I could easily get lost for hours. Don't get me started on any of the warrens available on the internet (or the internet itself for that matter)...