The items we've used so far were collecting data from some Zabbix agent or SNMP device. It's 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: These items require writing exact formulas and referencing each individual item. They're more flexible than aggregate items, but aren't feasible over a large number of items and have to be manually adjusted if the items to be included in the calculation change.
• Aggregate: These items operate on items that share the same key across a host group. Minimum, maximum, sum, or average can be computed. They can't 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.