System76 is a company that sells computers with a Linux OS pre-installed and made of hardware optimized to work especially with Linux(Linux will work on pretty much any hardware including apples). “Linux” in this context is a loosely defined colloquial term which refers to a large group of OS’s (the OS’s are also called Linux distributions/distros) which all use the same kernal component (this is the most important part of an OS) which is officially called the Linux Kernel. The actual OS’s can vary massively from one another POP_OS! is one of these Linux OS’s. You will have to pick a specific Linux distribution, which you can use to completly replace the current OS on any computer, including a MacBook, no virtual machine needed

Pop_OS! is system76’s inhouse Linux distro. It’s pretty good if you’re looking for a soft introduction to Linux, I’d recommend them too. You could also download it from their website if you wanted to install it on something else, but their laptops can come pre-installed with it.