(Psychological / emotional perspective)
The act of sacrifice, or rather of making our lives sacred, needs to be acknowledged and can be done through ceremony.
An altar is an appropriate place to carry out such ceremonies, so in dreams it signifies a special place of great meaning. What is placed on the altar is significant and can be interpreted in the light of your religious belief or lack of such belief. Psychologically, it is worthwhile considering what is being sacrificed or given up, either willingly or unwillingly, in everyday life.