It's called a container machine but it's a virtual machine. I quote from https://github.com/apple/container/blob/main/docs/technical-...

> container runs containers differently. Using the open source Containerization package, it runs a lightweight VM for each container that you create. This approach has the following properties:

> * Security: Each container has the isolation properties of a full VM, using a minimal set of core utilities and dynamic libraries to reduce resource utilization and attack surface.

> * Privacy: When sharing host data using container, you mount only necessary data into each VM. With a shared VM, you need to mount all data that you may ever want to use into the VM, so that it can be mounted selectively into containers.

> * Performance: Containers created using container require less memory than full VMs, with boot times that are comparable to containers running in a shared VM.

So: you build it as a container image and MacOS starts a VM to run it.

Edit: quite unusually for a container it runs systemd. They give an example "systemctl start postgresql".