The first telescopes used to peer into space were refracting telescopes. this means that you would look straight through the telescope from one lens to the other, to the image you were looking at. However, lenses used in these telescopes were blurry. It was soon discovered that if the telescope lenses were further apart, they would show a clearer image, and then telescopes began to get really long.
In the 1680's Isaac Newton designed a successful reflecting telescope. this type of telescope had a mirror inside that would reflect the image to a focus point. Newton found that this made the images of space much clearer to the viewer. since that time, humans have raced to build bigger and better telescopes.
nowadays, there are many different types of telescopes. there are radio telescopes, X- ray telescopes, infrared telescopes, gamma ray telescopes and ultraviolet telescopes.