It really hinges on these things called "control groups" and "namespaces," which are features of the Linux kernel. The "kernel" is the core computer program that interfaces with the hardware. MacOS has its own kernel. (If you install htop for mac, run htop at a terminal, press "t" to go into tree view, and scroll to the top, you'll see kernel_task, the representation of the kernel).

A "control group" (or "cgroup") is a feature of the Linux kernel that lets you create an environment with a fixed allocation of memory, CPU, and other resources. Aka a controlled group of resources. Whatever runs in here only gets the resources defined by whoever created the cgroup.

The other feature is "namespaces", aka a "process namespace." It's another feature of the Linux kernel that lets you create an isolated namespace for processes to run in. If you're a process running inside this namespace, to you, it looks like you're the only process on the system. You can run multiple processes in a namespace (Docker containers can run more than one process!)

So on Linux, to create a container, you basically use native Linux features to build this isolated environment, and run some process(es) in it. This is also why there are different ways to run containers (BSD jails), really what we're talking about is building an isolated environment.

As far as I know, the Mac kernel doesn't have these same features to create isolated environments, which is likely why Docker for Mac went with a full Linux VM, which includes the kernel. This is approaching the limit of my knowledge. I don't know what the Mac kernel is missing or what gaps or proposals there are to create a container-like environment. I also haven't worked with BSD jails or other technologies so I don't know how portable containers are between systems, if at all.