When 1,000 kWh of electricity is produced and pushed into the gird, 1 REC is created. This REC holds all of the green/environmental benefits of that energy. If you own that REC, you own that renewable energy. Its as simple as that.
Not only do RECs allow you to green your power, but they also incentivize new renewable energy development. When you buy RECs you are doing more than just helping your business, you are supporting a movement.