Simply explained, it's a way of spreading your plant out, so more of it gets light, and you can grow fewer plants in the area.
You put a screen, like 2 inch chicken wire, about 10 inches over your planting medium, and when the plant grows up to the screen, train the branches outward in all directions. As the shoots grow, continue training them by looping under and over the screen. When the screen is 2/3 full, induce flowerng and continue training. When the screen is full, the flowers will shoot up everywhere, filling the area with buds.
HTH