Whether or not MonoBehaviour collision messages will be sent by the physics system.
If this property is set to true, OnCollisionEnter, OnCollisionStay, and OnCollisionExit messages will be sent to the corresponding scripts that have these methods implemented.
If this property is set to false, no OnCollisionEnter, OnCollisionStay, or OnCollisionExit messages will be sent. This can be beneficial when only the Physics.ContactEvent is used to read contacts as this will stop the physics system from iterating simulation results.
Note: This does not affect trigger events.