Some of the actual differences get super technical. To switch to another OS, you can either buy another computer with it pre-installed, or install the new OS on an existing computer. You can dual boot (where you can install multiple OS’s one one computer, but you can only run one at a time, so you have to select which one when you boot the computer. To swap between the two, you straight up have to shut off the computer and select another one. You can also use virtual machines. A technically not correct explanation, is that you’re basically emulating another OS on your computer. You just need enough resources (specs) to run two OS’s at once, as opposed to dual booting where you solely run one OS at a time.
DOS is basically dead. It was the basis of Windows and was axed when XP came out. So outside of using legacy software on old computers (or emulating through DosBox) it’s essentially irrelevant. DOS was the “core” of Windows and was command line only, and Windows was the GUI (graphical user interface) to make it more user friendly. Part of the reason why some games have to be run in DOS mode was because Windows itself took up a lot of resources, so running in DOS boots your computer without Windows, and let you utilize more resources.
Unix and Linux are different “families” of operating systems, that share similarities under the hood, or were built off of an existing version of Unix or Linux. There’s no “pure” version of either, so when people say they use either Unix or Linux, they need to be more specific. It’s the equivalent of saying “I drive a truck”, well… what kind of truck? What model truck? Since Linux is heavily inspired by Unix (hence why it’s called a Unix-like OS), the lines can get blurry.
You won’t run into Unix much. Outside of MacOS, it’s pretty common as the custom operating system of enterprise hardware. So on a rack mounted server, it hosts Windows on it, but the OS to configure the hardware would be some variant of Unix.
With MacOS, since it’s a completely different OS from Windows, you can’t run Windows software on it. You have to have software specifically written for MacOS. So popular software like MS Office or Google Chrome have to be ported over. With that, it has exclusive software. It’s also part of the reason why gamers don’t use Macs, the lack of games. Macs (and anything that isn’t Windows) are immune to Windows viruses, because they’re written for well… Windows. Though that’s entirely due to the overwhelming market share of Windows. (Iirc it’s like 80%). So while your chances aren’t zero, you are less likely to get viruses
It is more efficient than Windows, because it only runs on a limited set of hardware variations, so you can easily optimize the operating system, as opposed to Windows or Linux where you have to make it compatible with a wide variety of hardware.
Macs also heavily cater to the creativity market in the hardware/software department, so if you hang around artsy communities, your likely hood of seeing a Mac is very high. It’s because Microsoft pissed those companies off in the 90’s, so Steve Jobs swooped in. I record music as a hobby, and Macs are less of a headache to use than Windows for it. A lot of the hardware is plug and play, while I have to spend a ton of time fiddling with stuff, or downloading various things to get my hardware to run on Windows.
With Linux, it has some of the benefits of MacOS (ie lack of viruses), but it’s more catered to “power users” than Windows and Mac, and is a lot more customizable. If you’re into tinkering, it’s for you. Using the command line (aka terminal) is very popular.
When you asked earlier what a distro was, it’s just the jargon for “variant” of Linux, and is short for distribution. So like my truck analogy earlier, saying distro, is like saying model. “I have an F150, I have a Silverado. Well Linux users will say “I run Ubuntu, I run Gentoo”.
Differences in distros will vary in a myriad of ways, and to make things more confusing, there are variations of Linux based off of an existing distro. Some differences will be the varying degrees of user friendlyness. Some versions require to do things only through command line, and others have it to where you never have to use it. Some also let you install software through their App Store, or just install it by double clicking the install file. Others have you build the installer yourself. Some of those make you wonder why do it the hard way, but some people just find it fun.
The reason why people claim Linux is better is that if you’re a power user, you have full control over it, and you can customize it yourself.
There is a degree of snobbery behind some users, because Linux is considered the “smart people OS”, so some people use it as a badge of “I’m smarter than you”. It also increases significantly alongside the difficulty of the distro. So a distro like Gentoo where you essentially have to program the OS yourself, and everything about it, they will let you know they use it without you asking.
If you’re still confused, feel free to pick whichever portion(s) you’re confused about, and I’ll break it down further.
In all honesty, there’s no “better” OS, it’s just what fits your use case.