CPU demand is a derived metric that is made up of multiple sub-metrics (in this case CPU usage, CPU ready, and so on), and is used to estimate the amount of CPU an object actually wants to consume. Although demand and usage are often identical, it is possible for demand to exceed usage; this would indicate resource contention. Demand is a useful way to manage capacity, since a virtual machine will rarely use all the CPU it has been configured with; this is the basic principle of over commitment. You will also find that demand usually matches the Usage % metric, which is observed inside the vCenter web client.

Recommendation for CPU demand:

As CPU demand accurately reflects the amount of CPU the workloads in your environment are requesting, regardless of what they have been allocated, we recommend enabling this container in nearly all situations.