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Add 32-bit/64-bit explanation
The Mac has had two main operating systems over its history: The "Classic" Mac OS versions 1 through 9, and Mac OS X (Ten, not Ex) which is now referred to simply as macOS. Classic was a closed-source proprietary OS, whereas macOS is based on an open-source Unix variant called Darwin. This Unix base helps with Linux compatibility.
The first several releases of macOS up to 10.4 Tiger contained support for Classic applications, but this was later dropped. Another major event for compatibility was the dropping of support for 32-bit x86 software in macOS 10.15 Catalina.
;CPU Architecture - PowerPC | x86 | x64 | Arm64
Rosetta was a software emulation layer that helped PPC applications to run on x86/x64 Macs. It was built into 10.4.4 Tiger, but was an optional install in macOS 10.6 Snow Leopard and not available at all for 10.7 Lion. Rosetta 2 currently facilitates x64 software to run on Arm Macs. While Rosetta performs very respectably for most software, it adds extra overhead which can reduce performance on demanding games and emulators.
Apple also introduced Universal Binaries that bundle software for different architectures into a single app bundle. For example, Universal 2 app bundles contain x64 and Arm versions of software in one app. This is very useful for portability, or for people who don't know or care about their Mac's specs. If you know what CPU your Mac has, the advantage of getting the specific version for your CPU is that it will have a smaller file size than the universal binary. However the size difference is usually tiny, so just using the universal binary is usually the way to go. ;CPU Processor Addressing - 32-bit | 64-bit64-bit CPUs offer a significant leap over 32-bit CPUs. The main advantage is that 32-bit CPUs can only address 4GB of memory, whereas 64-bit CPUs can address 16 Exabytes of memory (far more than is currently physically possible in a modern PC). However, this is not the only advantage. Often overlooked is the fact that 64-bit CPUs have a more modern design, with a modern CPU instruction set. They can often perform the same tasks faster and more efficiently than 32-bit CPUs. Macs first transitioned to use 64-bit CPUs with the PPC G5. There was no compatibility issue at the time, because the G5 had 32-bit backwards compatibility. But at the time IBM and Motorola (who designed and produced the PPC chips) had pretty much given up on the idea of producing desktop CPUs, so Apple had little choice but to transition to using Intel processors. Intel Core Duo processors at the time were much more power-efficient at the time, but they were 32-bit. So when Apple introduced Core Duo Macs, they sacrificed the advantages of 64-bit. This only lasted a couple of years, as the next generation of Macs shipped with Core 2 Duo CPUs, which were 64-bit. The next major event for Mac compatibility was the dropping of support for 32-bit x86 software in macOS 10.15 Catalina.
;Graphical Backend - OpenGL | MoltenVK | Metal
