Hi Krishna,
you may find the below note useful.
VM-VM affinity: This is useful when you require that 2 of your VM’s should always run together on an Esxi host. For E.g. Keeping front-end and back-end server of an application on same ESXi host to reduce network latency between the 2 VM’s.
Another use case will be running together same types of VM’s which are having same type of applications so as to get max benefits of transparent page sharing (TPS)
VM-VM anti-affinity: This is useful when you don’t want that 2 of your VM should run together. Keeping servers providing same kind of services on different host will provide resiliency
For e.g. You will not want your DC and ADC run together on same Esxi host because if that Esxi host goes down it can severely impact your environment as both DC and ADC server has gone down together.
Another use case will be running web-server farms or clustered DB-servers in a virtualized environment.
Also, keeping away 2 VM’s from each other which are very resource intensive to stop them from monopolizing resource usage.
You may find additional information from the below link.
vSphere 5.5 Documentation Center
Please share your feedback.