The explanation is that preemptible instances are VM instances that offer lower costs than regular instances but can be reclaimed by OCI at any time due to capacity constraints or after running for a maximum of 24 hours. Preemptible instances are ideal for short-lived and stateless workloads that can tolerate interruptions and do not require guaranteed availability or performance. Preemptible instances are billed by the second at a fixed rate that is lower than regular instances.