It runs on top of https://github.com/containers/libkrun. Similar to Firecracker but seems specifically targeted to making microVMs out of OCI containers (via CLI) as opposed to Firecracker which uses a downloaded kernel and rootfs and is managed via API ala https://github.com/firecracker-microvm/firecracker/blob/main....
But I'm no expert, just my armchair take on things.