We can distinguish between individual and combined visual elements. With individual we will refer to elements showing certain information in one container, such as a graph or a network map. While individual elements can contain information from many items and hosts, in general they cannot include other Zabbix frontend elements.
While the previous definition might sound confusing, it's quite simple—an example of an individual visual element is a graph. A graph can contain information on one or more items, but it cannot contain other Zabbix visual elements, such as other graphs. Thus a graph can be considered an individual element.
Graphs are hard to beat for capacity planning when trying to convince the management of a new database server purchase. If you can show an increase in visitors to your website and that with the current growth it will hit current limits in a couple of months, that is so much more convincing.