What is a Drip Loop?
An electrical service drip loop is a loop formed on the incoming feeder wires of your electrical service, before the meter. The overhead wires come to your service pole via the utility company. Out of the weather head on your service, you have three wires to connect to their wires. These wires should be left long enough to make a half-moon shape or a smiley face as it is.
What Purpose Does It Serve?
The reason for having a drip loop on an electrical service is to allow any rain or moisture, that may make contact with the wires, a place to go away from the weather head and the electrical connection to the utility company's wires. Water or moisture running down the service pipe or running into electrical connection points would spell costly repairs for you in the future.
Freshwater Aquarium guide, Shirlie Sharpe, explains how to and not to drape your electrical cords to an outlet. This insightful article deals with indoor drip loops when connecting electrical devices to an outlet from an aquarium.