A student's hobby project now runs most of the world
In August 1991 a Finnish undergraduate named Linus Torvalds posted a message to an internet newsgroup about an operating SYSTEM he was writing. He was careful to lower expectations: it was just a hobby, he wrote, and it would not be big and professional. He was asking what features people might like.
LINUX now runs the overwhelming majority of the web servers you visit, every one of the world's fastest supercomputers, most of the internet's plumbing, and — inside ANDROID — the majority of the phones on Earth. Anyone can read its code and change it, which is exactly why it ended up everywhere: no company had to agree, and no licence had to be bought. It is the most consequential hobby project in computing history.
Your desktop is a metaphor from the 1970s
There is no DESKTOP inside a computer, no FILES, no folders and no bin. Those are borrowed from an office, and the borrowing happened at Xerox's research centre in California in the 1970s, on a machine called the Alto. The idea was that people already understood paper, so the INTERFACE should pretend to be paper — a document you open, a folder you put it in, a desk you leave things on.
It worked so well that fifty years later we still use it, long after most people stopped using actual filing cabinets. Every ICON, MENU and TASKBAR is a small piece of theatre standing in for something the machine does quite differently underneath, and children now learn the metaphor from the computer rather than the office it was copied from.
The referee you never see
Open a game and it does not talk to the screen, the speaker or the storage. It asks the operating SYSTEM, which is refereeing every PROGRAM at once — handing out slices of processor time, keeping each one's memory separate so a crash in one does not take down the rest, and deciding who gets to write to the disk next. At the centre sits the KERNEL, running from the moment you BOOT until the machine goes off.
That refereeing is why a RESTART fixes so much. Programs gradually leave things in a muddled state, and starting over hands every one of them a clean slate. It is also why a DRIVER matters: the system cannot possibly know how every printer or graphics chip works, so each device brings a small translator with it. Most of what SETTINGS, INSTALL, UPDATE and BACKUP actually do is manage that quiet arbitration on your behalf.
Three families, three different problems
The big names are not really competing on features so much as solving different problems. WINDOWS has to run on machines built by hundreds of manufacturers in combinations nobody could test in advance, which is why it carries an enormous library of DRIVER code and why installing SOFTWARE occasionally goes strangely wrong. MAC runs only on hardware made by the same company that writes it, a much shorter list, which buys tidiness at the cost of choice.
ANDROID took a third route: give the system away, let each phone maker adapt it, and accept that every handset ends up subtly different from the next. Each approach trades control against reach, and every irritation people complain about — a missing DRIVER, a MENU that moved, an UPDATE that changed the LOGIN screen — usually traces back to which of those bargains the maker struck.