Compound templates allow the Gen.IT user to take a small template (eg, a configuration for a single switch port or single L3 SVI), and define how many times the template is repeated. In addition to that, variables or IP address can be increment at predefined intervals for each iteration of the template.
The actual values defining the number of repeat cycles, variables etc can be looked up from other places within the spreadsheet.
Compound Templates may also contain Include Templates.
Please see the the user guide here for further information and examples.