What is consciousness? What are some examples of different states of consciousness?

Consciousness. Consciousness = awareness; this can be at different levels. Alert: fully conscious and aware of their environment. Drowsy/lethargic: awake, but fatigued & can fall asleep easily if not stimulated. Obtunded: even less alertness, with decreased responsiveness and interest in their environment. Stupor: not responsive except to vigorous stimulation. Coma: not arousable at all.