A resource is anything that can be scheduled using a calendar, such as a conference room, or a projector. There is a separate resource LDAP entry for each such item. Create the LDAP entry and its associated calendar using the appropriate tools:
For Schema 2 - Use Delegated Administrator to create the resource LDAP entry, and the Calendar Server utility resource to create the calendar.
For Schema 1 - Use the csresource create command which creates both the resource LDAP entry and the calendar.