Items are the ones that gather data from a host.
Once you have configured a host, you need to add some monitoring items to start getting actual data.
An item is an individual metric. One way of quickly adding many items is to attach one of the predefined templates to a host. For optimized system performance though, you may need to fine-tune the templates to have only as many items and as frequent monitoring as is really necessary.
In an individual item you specify what sort of data will be gathered from the host.
For that purpose you use the item key. Thus an item with the key name system.cpu.load will gather data of the processor load, while an item with the key name net.if.in will gather incoming traffic information.
To specify further parameters with the key, you include those in square brackets after the key name. Thus, system.cpu.load[avg5] will return processor load average for the last 5 minutes, while net.if.in[eth0] will show incoming traffic in the interface eth0.
Proceed to creating and configuring an item.