A mandala is a symbolic diagram, usually including a circle, designed to show the relationships between Buddhist deities. The center circle contains a bodhisattva, a compassionate being who could at any moment become a buddha, but who has postponed his own enlightenment in order to assist others along the religious path.
The bodhisattva is surrounded by other deities; in the corners of the squares are demons the seeker must confront. Around the edges are monks. Where are the gates a seeker after enlightenment must go through?