The Scheduling Affinity option gives you detailed control over how virtual machine CPUs are distributed across the host's physical cores (and hyperthreads if hyperthreading is enabled). This panel does not appear for virtual machines in a DRS cluster or when the host has only one processor core and no hyperthreading.
Using CPU affinity, you can assign a virtual machine to a specific processor. This assignment allows you to restrict the assignment of virtual machines to a specific available processor in multiprocessor systems.
For potential issues with CPU affinity, see the vSphere Resource Management documentation.