The items we have used so far were collecting data from some Zabbix agent or SNMP device. It is also possible to reuse this data in some calculation, store the result and treat it as a normal item to be used for graphs, triggers, and other purposes. Zabbix offers two types of such items:
Calculated items require writing exact formulas and referencing each individual item. They are more flexible than the aggregate items, but are not feasible over a large number of items and have to be manually adjusted if the items to be included in the calculation change.
Aggregate items operate on items that share the same key across a host group. Minimum, maximum, sum, or average can be computed. They cannot be used on multiple items on the same host, but if hosts are added to the group or removed from it, no adjustments are required for the aggregate item.