Water filters are for people who want their water to be completely clean and healthy (and who wouldn't now that you have this beautiful faucet). No matter which area of the world you stay in and how you get your water, there are always invisible organisms, bacteria and other contaminants present in the water not to mention all the pesticides, chemicals and industrial wastes that go into the soil and natural water sources daily.
Water filters come with a variety of filtration mechanisms such as Reverse Osmosis, CTO or Chlorine, Taste, Odor filter, activated Carbon filter and so on. Each type of filtration has its own purpose. The best type of water filter uses more than one level of filtration to ensure that the water is completely pure and drinkable. Most of the better water filter models in the market can get rid of pollutants up to 0.3 Micron in size. These water filters usually come costlier than other variants but you will not have to bother about the quality of water at your home again.