Clear glass means clear photos
I'm not going to go on at length here. It's a lens cloth. It's not all that complicated.
The reason that there is even a section on it is that a lens cloth is a great low-cost accessory for your digital camera.
Even if you are meticulously neat, stuff always manages to get on your lens. For example, if you take your camera to the beach, the salt particles in the air will attach themselves to your lens. The next time you got to take photos, everything might look a little hazy. If this is what you want, then no problem.
The reason that they make special lens cloths is because a standard kitchen towel just won't do. In the section on filters, I mention that you can get a UV filter to protect your lens. A UV filter protects your lens from dust and scratches.
The reason to have a lens cloth is so that you don't scratch up your filter (or your lens) every time you clean it.
How often will you have to clean it? Depends. There is one sure thing: camera lenses get gummed up especially fast in homes with small children. With a lens cloth at your side, a gummy lens will never be a problem.