Product review (5 stars): Inexpensive way to buy a water filter for your fridge, if it has a water and/or ice dispenser. Change it regularly.
We have a General Electric ESS25 fridge that has a water and ice dispenser. This is the filter for the water/ice dispenser. We change it every six months.

Our house has a water softening system, and also a reverse osmosis system under the kitchen sink. So, our water is pretty good. We use the R.O. water for cooking and drinking, and thus rarely dispense cold water from the fridge. Still, we use the fridge's ice often, and the filter keeps the ice tasty (don't want it ruining the drinks) and also keeps the ice-making mechanism clean.

These filters are a fortune to buy retail. We buy them in three-packs from Amazon for a lot less.

HINT 1: Newer fridges tell you when it's time to change the filter. Ours doesn't. We settled on every six months because we only use it for ice, not for water. However, I'm told that if you notice that your fridge water has a smell or doesn't taste good, that indicates that it's time to change the filter. It all depends on how much water/ice you use, and how clean your home water supply is.

HINT 2: When you change the filter, write the date of the change on the filter with a sharpie. Otherwise you'll have no idea how old it is!