Multi-graph reports combine data from different devices and components into a single report. You can create a graph definition and have it drawn once for each of a group of devices and components that you define. Alternatively, you can combine the data for those graphs into a single graph.
The groups of devices and components you assemble are called "collections". Specifying the graph definition to apply to collections is done through graph group objects. Multi-graph reports include their own graph definitions, and thus do not use the graph definitions that are defined in monitoring templates. To create a report that includes graphs defined on templates, use a Graph report instead.