Legacy Exchange define information store level items

Select this option to identify the information store backup configuration. The Information Stores display renders a tree-view of the Microsoft Exchange server stores that are available for backup. Select a group or an individual store to backup. The Default backup option backs up the storage group and all of its stores. The actual file name for the default backup option is default.bkf. 

The Group backup option allows you to select multiple individual stores to back up. One .bkf file is used to back up each group. The Single backup option is used to back up a single Exchange information store. Differential backups and restores can only be performed at the group level. The backup or restore operation is not permitted for a differential backup consisting of a single store.