You gain the ability to Waterbend which can be used to manipulate Water, the element of change, starting with only knowledge of the basics but holding prodigious talent, enough to become a master Waterbender on your own and even invent new Waterbending styles and applications like healing.
Waterbending relies on the presence of Water, which can be quite restrictive as a beginner, but with mastery can be accessed through unorthodox sources like sweat, the moisture in the air, plants, and potentially even blood. Waterbending is spiritually connected to the moon, and as such is strongest at night, during the full moon, during winter, and near the north pole and south pole, but weaker during the day and close to the equator, and powerless during lunar eclipses.