"Storage pools” are storage resources managed by a VM host. A storage pool is a given amount of storage set aside for use by VMs. A pool can be organised into storage volumes, assigned to VMs as individual block devices. More information is available for both libvirt and LXD storage pools.
For LXD VM hosts, each VM can be assigned a single block device from the storage pool.
The MAAS web UI displays information about each VM host’s storage pools so you can understand your resource usage at a glance: