nerdctl is just a new client to target containerd.
Containerd has been around a long time, it was originally part of Docker itself, but was separated out and is now a standalone project.
Docker uses containerd as part of it's standard deployment.
Containerd is a long running daemon (similar to dockerd), so that's where the difference lies in that podman (in it's default setup) doesn't have a long running daemon.
The closest analogy to containerd in RH land is CRI-O.
Containerd has been around a long time, it was originally part of Docker itself, but was separated out and is now a standalone project.
Docker uses containerd as part of it's standard deployment.
Containerd is a long running daemon (similar to dockerd), so that's where the difference lies in that podman (in it's default setup) doesn't have a long running daemon.
The closest analogy to containerd in RH land is CRI-O.