There are many different types of home water treatment devices on the market. The one that is right for you is the one that addresses the specific problems you are having with your water. When interpreting your water analysis results, remember that the presence of a contaminant does not always mean that the water needs to be treated. 

If you receive your water from a public water system, call the operator for a report on the water quality (Consumer Confidence Report) which will show what the water is tested for and the results.

If you are considering water treatment to remove a contaminate related to a health condition, keep in mind that removing the source of contamination or replacing the unsafe water supply with a safe one maybe more appropriate than treating the water. 

In general, there are "point-of-use" and "point-of-entry" treatment systems.

Point of use (POU) devices treat the water at the point it is going to be used, usually for drinking or cooking purposes and only one tap in the house may be connected to this filter (such as reverse osmosis or charcoal filters attached to the top of faucets).

Point of entry devices (POE) treat the water as it enters the home and is then distributed all the taps in the home (such as water softeners).