Google Cloud's virtual machine service (IaaS). It provides highly configurable VMs with options for CPU, memory, and storage. Offers Spot VMs (formerly preemptible): low cost, but they can be interrupted.
In CDL it's the equivalent of EC2 (AWS) or Azure VMs. An example of IaaS on GCP. Spot VMs are up to 91% cheaper but Google can reclaim them with 30 seconds' notice.
Compute Engine is a concept that can show up on the exam. Check the full guide to see it in context.