The mandala offering is a Tibetan Buddhist practice in which the practitioner symbolically offers the entire universe, everything precious and beautiful in it, to the enlightened beings, as an act of boundless generosity and a means of accumulating the merit needed to progress on the path. Using a special round base and heaps of rice or grain, often mixed with jewels and precious substances, the practitioner constructs a symbolic model of the cosmos as pictured in Buddhist cosmology, the central world-mountain, the surrounding continents, the sun and moon and all the wealth of gods and humans, reciting a liturgy that presents this whole imagined universe as a gift. Having offered it, the practitioner sweeps the heaps away and builds it again, repeating the offering many thousands of times.
The practice is one of the foundational preliminaries, the ngondro, that a student completes before undertaking the higher tantric practices, undertaken alongside the accumulation of prostrations and mantra recitation. Its purpose is understood on several levels: it cultivates the perfection of generosity by training the practitioner to give away, in imagination, the greatest gift conceivable; it counteracts attachment and grasping by the repeated act of offering and letting go; and it builds the vast store of merit that the tradition holds necessary to support insight and realisation. That what is offered is not real wealth but a symbolic construction is essential to the practice, which works upon the mind of the giver rather than transferring any actual property, teaching a generosity unlimited by what one happens to possess.