'Shri' or 'Shree' stands for Lakshmi and 'yantra' stands for device. Shri Yantra is a device that helps invoke the power of Lakshmi into our lives.
In tantrik tradition, this device is represented in a geometric format. It is a diagram of six intersecting triangles. The three upward pointing triangles represent the male energy and the three downward pointing triangles represent the female energy.
The intersections of the six triangles represent points of concentrated energy that signify fertility or creation. A 'bindu' or dot in the middle of the diagram is said to be the point where the Goddess Tripursundari or Lakshmi's female creative form exists.
The whole geometric design is encased in a lotus design, representing the universe or creation. The yantra symbol thus represents the creative aspect or fertile aspect of the cosmos.
The Shri yantra is a very powerful symbol that dispels all negative energy from its vicinity and fills it with positive, progressive, and auspicious energy.
It is believed that Goddess Lakshmi has great affection for the Shri Yantra and blesses thoes who possess it.