If this is true, the Simulate Rigid Bodies node treats the corresponding particles as passive. This attribute is necessary to use particles as obstacles, because all particles must be in the same point cloud to interact in a rigid body system.
The PointVelocity and AngularVelocity of a passive rigid body are not taken into account during a collision, and are unchanged after a collision. It's as if the passive rigid body has infinite mass. However, the DynamicFriction and Elasticity of both the active and passive particles are taken into account during a collision.
Note also that the Simulate Rigid Bodies node does not update PointVelocity based on Force if IsPassiveRigidBody is true. If required, you can filter these particles and calculate a new velocity for them based on F = ma.
See[ ] for information about using this attribute.