Point-of-use filters treat water only where and when you need filtration, such as at your kitchen sink or refrigerator. Point-of-use filters are often more economical, but if you wish to treat water at multiple locations in the home, you will need to buy a filter for each location. Point-of-use filters are a good choice when you want to remove contaminants that originate in your home plumbing (such as lead).
Point-of-entry filters treat all water that enters your home. This will include your kitchen sink and refrigerator, of course, but also your toilet water, bathwater, laundry water, and in some cases water at your outside spigots. Point-of-entry filters may be more expensive, and will not address issues in the plumbing that cause problems after the filter (such as lead solder in your household pipes). If you use a point-of-entry filter that removes chlorine, it's important to keep in mind that you are removing the disinfectant in your tap water. This could lead to bacterial growth.