The scrogging (screen of green) method is used when the grower has limited space.
A net or chicken wire or similar is placed above the plants so when the plants grow through it they receive instant support. Plants are not usually grown very big with the scrog method, instead, lots of small plants are crammed into the space and flowered when they are still only small. The idea of it is to get a canopy of buds which all receive the same amount of light. It's probably the most efficient method for small grow rooms. The scrog method itself does not effect potency or flowering time, yield is effected because of the way the plants are grown.

hope this helped.