Tap water can usually have a variety of contaminants within it. This does not necessarily mean that they will harm you, of course, but they may have other impacts. For example your shower water may make it difficult to get a good lather going with soap. It may also make your drinking water taste a particular way.
This is where you might benefit from a water filter. Water filtration systems can be set up almost anywhere within your home. They may be more or less visible depending upon where you want them. They will pull any number of contaminants from your water that will make it more pure. This means a cleaner taste and a better feel to it.
Not only that, but they also usually require replacement filters to come periodically. This replacement system can be set up with the company you purchase the system from typically and can be fairly convenient. The replacement programs do tend to vary from company to company.
Of course this can also mean benefits to the environment. If you decide to use a water filtration system for cleaner tap water then you may choose simply to drink that rather than, say, bottled water. This can add up over time and result in a significant reduction in the amount of plastic you have to throw away or recycle.