Individual oxygen atoms are very very grabby; they’re stage-5 clingers on PCP. They’re straight-up homewreckers, and they cannot and fucking will not be alone. They need a friend or two, and they will go and rip molecules apart to take them because fuck you.

Now, if there’s nothing else available, they’ll pair up with another oxygen atom, and form O2, what people normally call oxygen; the stuff you find in the air.

But it’s an uneasy alliance, and the bond angles are all wrong so it’s kind of spring-loaded.

And the same goes for lots of other molecules - carbon-carbon or carbon-hydrogen bonds ferinstance are also kind of tense and uncomfortable; it takes a surprising amount of energy to snap them into place, like building a tower of interlocking mousetraps.

So smack an O2 at reasonably high speed (or in other words, at a high temperature) at big structure of carbons and hydrogens, and it’s fucking chaos.

The oxygen-oxygen bond splits, and the two halves grab the other atoms, ripping the structure apart and releasing all the energy that went into spring-loading those bonds.

The main byproducts are CO2 (a carbon with two oxygens) and H2O (an oxygen with two hydrogens), both of which are very low-energy, strong bonds.

They’re both gases, and all that energy leftover is released as heat, which does two things:

• raise the temperature enough to do the same thing with even more O2s, causing a chain reaction
• heat up the released gases (and any bits of random gunk that break off with them) so much that they glow red hot, just like hot iron.

So you get plumes of glowing hot gas-and-particles streaming off the stuff that’s burning - and hot air rises, so the plumes point upwards.

But they also cool down quickly in the air, below the glowing-hot point, and that’s why flame has a shape: the boundary is how far as they get while still hot enough to glow.

Of course, hydrocarbons and carbohydrates aren’t the only things that burn, there’s lots of other molecules you can do this to, and the same principle applies. It’s just that carbony things tend to burn easily and well, and we’re surrounded by the stuff because that’s what living things are made of, so that’s what you tend to see being on fire the most.

Okay:

You don’t have to deal with scripting and command-line stuff, but all the major tinkering under the hood depends on it. The amount of customisation and tinkering is fairly infinite, so past a certain point you just can’t build graphical stuff to cover every single possible choice - and that’s where the gibberish comes in.

Baseline concepts:

‘Operating system’ means different things in different contexts, and this can be confusing.

Context 1: technically correct

Your computer has a big chip that runs programs, and a bunch of hardware that actually-does-stuff: network card, graphics card, disk drive, mouse, keyboard etc. Programs need to talk to the hardware and make it do stuff, or else they don’t actually… do… anything.

There’s two problems with that:

There’s a gazillion kinds of hardware out there, that all has its own language for talking to it, and your program would either only run on one EXACT set of hardware, or it would have to speak all gazillion languages and be too big to fit on your machine.

The second problem is that in order to do more than one thing at a time, you need a bunch of programs all running at once, and they all need to use the hardware, and without something to coordinate the sharing, they’ll all just fight over it and everything falls down in a tangled heap.

A good analogy for this is a restaurant. They aren’t just public kitchens where you can just wander in and start preparing your own meal, taking ingredients/equipment/space however you want, then just carry it to whatever table takes your fancy - and you definitely can’t have all the customers doing it at once. Especially if they don’t know how all the equipment works, where the different ingredients are kept, etc - it would be an absolute disaster, and there would be fights, injuries, fire and food poisoning.

So instead there’s an agreed-upon system with rules, and people that do the cooking for you. You make a reservation or queue at the desk, you are told which table you can have, you go sit there and a waiter brings you a menu. You pick the food - and depending on the place, maybe ask for customisation - then wait and they bring it out to you, then you sit there, eat it, then leave.

That system-with-rules is the operating system, or more specifically the operating system kernel. Any time a program wants to do more than think to itself, it has to asks the OS to do it, and bring it the results.

In this analogy, fundamentally different operating systems (windows / linux / OSX / android / etc) would be like different kinds of (5-star / sushi-train / pizza place / burger joint / etc) that have different rules and expectations and social-scripts to interact with them. A program written for one OS would have no idea how to ask a different OS for what it wanted, and wouldn’t be able to run there.

Context 2: what people usually mean

It’s all well and good to have a machine that can run programs and do things, but the human sitting in front of it needs to be able to interact with the thing, so you can poke buttons and move files around and move windows and stuff.

And so there needs to be a crapton of programs all working with each other on the thing to provide all this functionality, and the whole user experience - preferably with a consistent design language and general expectation of how everything should work: you need a desktop environment.

In restaruant terms, this would be the specific brand/franchise/corporate-culture that runs the place. Yes, the general idea is that it’s a burger joint, but specifically it’s a mcdonalds, or a wendy’s, or whatever that homophobic chickenburger place is called - it’s got the decor, it’s got the layout, it’s got the specific combo meals, etc etc, the same uniforms, the same staff policy, etc.

Now here’s the thing:

Let’s say there’s only one sushi franchise in the world. That’s like Windows - there’s updates new versions and some slight variations (server versions aside), but you walk into one, you’ve walked into them all. There’s one Windows kernel, and one windows desktop environment that goes with it.

And say there’s only one pizza-place franchise in the world, and they all look the same, have the same menu. That’s like OSX: there’s one kernel, and similarly one OSX desktop enviroment to go with it. A mac is a mac, and it does mac things.

But linux… linux is different. With Linux, it’s there’s 900 different burger-joint franchises in the world, and literally anyone can go start a new one if they want to put the time into designing one from the ground up. The paradigm is the same - order at the counter at the back, menus on the wall overhead, grab bench seating wherever or get it to go - but every place can design the look and feel, the menu, the deals, the other amenities, the staffing structure, etc.

And the different franchises - that’s what distros are.

It’s the set of programs all working together that create a whole working enviroment, but everything uses the standard kernel to actually get stuff done. If your program can run in one linux distro, then it should be able to run in a different one, because your program uses the same standard set of requests in order to do things.

The windows and the menus and the desktop apps and the way the interface behaves and how you configure everything can be different, but the core functionality that the software uses, is the same.

Now, for the most part, Windows is like NO USER-SERVICEABLE PARTS INSIDE, all the fiddly internal bits are carefully hidden away and made deliberately opaque. You don’t need to know, we don’t want to tell you, we’ll let you change the wallpaper, but for everything else, we decide how it’s wired up. If you want it to do things slightly differently to suit your own workflow, tough.

Macs are kind of the same deal: for the most part it’s no-touchee, you’ll break stuff. Just push the very shiny buttons and be happy that everything Just Works ™.

But Linux… doesn’t seal anything in plastic. All the gubbins are not only there on display, they’re mostly all human-readable and human-tinkerable with. Instead of mysterious monolithic chunks of software communicating with each other via hidden channels, with configuration in databases you don’t get to see… it’s mostly scripts you can read and tinker with, and plain-text config files you can edit, all writing useful details in highly-visible log files that you can read through when things don’t do what they’re supposed to.

Now with a lot of distros, you absolutely can just push buttons and treat the thing like a Windows box, and never have to tinker with the fiddly bits. You’ve got a browser, you’ve got apps, you’ve got games, it just does the thing. But if you want to start getting technical, you absolutely can - unlike windows or mac.

But this very ability to configure and tinker and patch bits on - and the fact that most distros don’t have a gigantic microsoft-sized coordinated team all following one shared vision, but are wired together like a kind of junkyard frankenstein from thousands of separate teams as a labour of love - means that occasionally you will need to get technical to deal with small annoyances or use-cases they didn’t think of.