Refractor telescopes help you to view the heavens by using lenses to amplify and magnify images in the night sky.  As shown in the simplified diagram below, light comes into the telescope through the Primary or objective lens.  It then is directed to the eyepiece and onto your eye.  A few advantages of refractor telescopes are that they are compact, lightweight and easy to transport.  They also require little to no maintenance.  On the other hand, in general, they are a little more expensive than reflector telescopes, especially when getting to the more advanced telescopes.  Also, chromatic aberrations are inherent in lenses, and in order to correct this problem, an apochromatic lens is needed and that adds expense.  All in all, a refractor telescope is an excellent choice for the beginner or advanced astronomer.  You can read more about refractor telescopes in this article.