Podman has a few tricks up its sleeve that Docker can't do. Among other things:
- `--rootfs` lets you start a container from a directory instead of an image
- You can configure alternate container storage locations, e.g. to share a common library of container images among multiple machines over NFS
- As previously mentioned, it has the k8s-like notion of "pods" which are multiple containers sharing namespaces with each other
- It will play nice with systemd, both inside and outside of containers, and can generate systemd services for containers
I think the last point is really why Podman exists in the first place; IIRC, Red Hat's developers made a valiant effort to get patches into Docker to improve its cooperation with systemd, but the folks working on Docker weren't interested. If Red Hat's patches to Docker had been upstreamed, Podman might not exist.