tl;dr: macOS Container Machines run full Linux environments (with init/systemd) from standard OCI images, automatically mapping your macOS username and home directory into the VM so repos and dotfiles are shared between host and guest. You can edit on macOS while building/running inside Linux, spin up multiple machines for different distros (Alpine, Ubuntu, Debian), and run real system services like Postgres via systemctl. Custom images work as long as they include /sbin/init, with a `container machine` CLI (aliased `m`) for create/run/stop/inspect operations.