These terms refer to the type of water filtration system the water dispenser uses. RO stands for reverse osmosis while UF stands for ultrafiltration. Tap water can be exposed to many contaminants, including chlorine and bacteria, and each type filters differently:
Reverse Osmosis (RO) - pushes water through a semipermeable membrane. The membrane allows water to pass through but not larger molecules, like bacteria, salt, minerals, and nearly all dissolved substances.
Ultrafiltration (UF) - uses a semipermeable membrane to prevent solid particulates from filtering through. An ultrafiltration system can filter out a variety of impurities but does not remove dissolved substances. Ultrafiltration may also leave minerals present in the water.
Each filter system can help improve water quality.