Host baseline groups are useful when you have to perform an upgrade. Also, post upgrade, you may need to install patches that were released at a later date than the host upgrade or an extension (for example, a driver upgrade) that will make the server hardware compatible with the newer upgrade.
It is a requirement that you already have the required ESXi Image imported. Read the recipe Importing ESXi Images for instructions.
The following procedure will help you create a host baseline group: