Group
Creates simulation object groups.
Groups can be used for two main purposes. First, affector relationships can only be set up between groups of objects. See 
Affector help for more information on affector relationships. Second, object groups can be used instead of complicated object masks to refer to sets of objects.
Using Group
Click the
Group button on the Drive Simulation tab.Select the dynamic objects to group and press Enter to confirm your selection.
For specific parameter node help see the Group help.