This page provides information on the Active Bodies component.
Overview
The Active Bodies Solver is used to specify the scene geometry which will partake in the Active Bodies simulation. When an object is selected as an Active Body, the simulation both influences and is influenced by the Active Body's movement. Mutual interaction between the Active Bodies themselves is not supported yet. Interaction between Active Bodies and the Phoenix FD Fire/Smoke Simulator is still not supported.
The Active Bodies Solver also sets up global simulation parameters which affect all Active Body objects in the Interaction list, in contrast to the Phoenix FD Node Properties which are unique for each Active Body. This way you can have several Active Body Solver nodes, each with their own set of Active Bodies with different rigid body behavior for each set.