Based on site location or resource allocation, host groups are designed to group virtual machine hosts.
When you have a host group structure, the following settings and resources will be allocated at the host group level:
Placement rules
Host reserve settings (CPU, memory, disk I/O, disk space, and network I/O)
Dynamic Optimization and Power Optimization settings
Network resources
Storage capacity allocation
PRO configuration
Custom properties
A host group will also allow you to do the following:
Assign the groups to delegated administrators and the read-only administrators' roles, and then members of these user roles will be able to view and/or assign fabric resources
Create a private cloud, assign host groups to it, and then allocate resources from the assigned host groups to that private cloud