RO - Reverse Osmosis
UV - UltraViolet
UF - UltraFiltration
RO water purifiers use the process of reverse osmosis to remove excess amounts of ions from the water and makes it safer to drink. Water contains ions like Magnesium and calcium, which are essential for our body, but if the water contains these minerals in excess it may harm your body.
RO technology could reduce the amount of excess solids in the liquid, but it does not kill the germs present in the water. To kill and to remove bacteria, UV water purifiers are used. UV water purifiers kill the germs by passing the water through ultraviolet radiations.
Again, the water purifier with UV technology could only kill the germs but may not remove excessive ions from it. So, the best solution is to get an RO plus UV water purifier that fulfills both your needs.
The Ultrafiltration or UF is nothing but a fiber threaded membrane that removes large solids and dispersed material from the water. The UF membrane is generally used before the RO filtration to reduce the load and increase the life of the RO membrane.