What a softener does
A softener exchanges hardness minerals for sodium or potassium as water passes through a resin tank. The result is less scale in pipes, fixtures and water heaters, and soap that lathers more easily.
It does not remove chlorine, bacteria or most other contaminants.
What a filter does
Filters trap or absorb what they are designed for. A whole-house carbon filter improves taste and odor and removes chlorine. A sediment filter catches grit. A reverse osmosis system under the sink treats drinking water for a much wider range of contaminants.
Start with a water test
A test shows hardness and what else is in the water. Treating a problem the water does not have wastes money, and the wrong equipment can leave the real problem in place.