CPU Affinity

Hello,

I have read about setting CPU Affinity for VM in vmWare but i am not clear with the concept.

Please can you explain it in detail with an example scenario, when this should be used ?

What i understood is by setting a CPU affinity on the virtual machine we limit the available vCPUs on which the virtual machine can run. But i am not able to understand why  we need to limit the available vCPUs for a VM.

eg. Suppose a VM has 4 vCPU then what will be the benefit if we create CPU affinity for 2 vCPUs only and what will happen to rest of vCPUs. Will they get used ??

Also, how this will be linked with physical CPU?

Thanks,

Bubbey