A mandala is the spiritual map of the universe in Buddhism. In Sanskrit, it actually means circle, for the entire universe is believed to exist within a mystic circle.
In Buddhist practice, there are various specific methods to accumulate merits, which is the fuel for the actual inner practice of spiritual transformation.
The five great preliminary practices are well-known to do just that. They are water offerings, prostrations, Vajrasattva practice, Guru Yoga and mandala offerings.
Mandala offering is a complete meditation of visualising a universe in the form of a mandala that is purified and offered up to the Buddha or one’s lama who is inseparable from the Buddha.
The complete mandala offering requires one to have a mandala set along with precious jewels or grains of any sort to represent it. There are specific ritual verses and meditations to go along upon making the offering. When not in use, it should be covered in silk or any piece of clean cloth and stowed away respectfully.
Mandala offerings generate a lot of merit for the practitioner to gain spiritual insight and understanding into the teachings and also to gain the ability to see Buddhas directly.
Lama Tsongkhapa is renowned to have performed 1.8 million mandala offerings in a closed retreat to gain a clearer understanding of the most profound Buddhist teachings of Madhyamika and Guhyasamaja. Upon completion of his retreat, he gained the insight and a vision of Maitreya.