Podman and Buildah for Docker Users

I was asked recently on Twitter to better explain Podman and Buildah for someone familiar with Docker. Though there are many blogs and tutorials out there, which I will list later, we in the community have not centralized an explanation of how Docker users move from Docker to Podman and Buildah. Also what role does Buildah play?

Is Podman deficient in some way that we need both Podman and Buildah to replace Docker?

Source: redhat.com