Advaita (nonduality) is a word that is used to indicate the nature of Reality, which literally means “not two”. It means that, in spite of appearances, there is only one principle operating, and it is the cause and effect of everything that is. You can call it Consciousness, Awareness, God, Being, Love, Intelligence, Knowing, Happiness, Freedom, Truth, or whatever you want. You can call it your Self, because that’s what it is. Because it is limitless words are inadequate to describe it, but that doesn’t mean that wielded by a competent teacher they are unable to reveal it.
Ignorance is the belief that I am small, limited, inadequate; that I need something or someone to complete me. It shows up as any belief, thought, emotion, fear or desire which doesn’t correspond to the truth: that I am unborn, whole, complete, limitless, ever present, all pervasive, nondual, actionless, unconcerned, ordinary awareness; that I am fullness itself. The practise of knowledge is to monitor the mind at all times, and to consistently refute ignorance in the light of the truth, until the ignorance is destroyed. It means taking a stand in awareness, as awareness.
Enlightenment is knowing that I am everything that is. And that’s it, really.