You simply fill a plastic pop bottle with water, screw on the plastic adapter, set the terra cotta stake in the soil next to your plant, and insert the adapter into the stake. Water seeps slowly and steadily through the semi-porous ceramic, wicking into the soil below the surface for up to two weeks. At a glance, a low water level in the bottle tells you it's time for a refill.
An efficient, convenient watering system, it is also an excellent way to keep transplants healthy until the roots are established.