Voidness as a quality of consciousness , means simply that one cannot identify them as one's own self or having anything pertaining to one's own self...
Voidness as a mental state, means a mode of perception in which one neither adds anything to nor takes anything away from what is present, noting simply, "There is this."
This mode is achieved through a process of intense concentration, coupled with the insight that notes more and more subtle levels of the presence and absence of disturbance.