Altar refers to the most sacred spot in any place of worship. It is the spot to which the Power from Above descends before disseminating to all other parts of the place of worship. The Power from Above strikes the altar table and from there spreads to fill the hall of worship. The Altar must be kept spiritually pure at all times and only those who are able to keep their thoughts pure should be allowed to serve at the altar.
We human beings too have an altar within ourselves that should serve as the purest spot for the worship of God. This is our intuitive perception. If this is kept pure at all times through the exercise of good volition, then we are directly connected to the spiritual realm and can sometimes feel within us the nearness of God.