Hyperopia or Farsightedness is a condition in which the distance between the cornea and the retina is too short or the actual shape of the eye is too flat. This causes light images to focus behind the retina, causing blurred vision.
The eye functions by focusing images i.e. the book on the left in the picture. There are two ocular structures that achieve this focusing, the cornea (or the clear window of the eye) and the natural lens (much like the lens in a camera).
Together they focus or compress the parallel light rays onto the retina (back structure of the eye, much like the film in a camera). The image is displayed on the retina and a photochemical reaction occurs. The image is then transmitted through the optic nerve to the brain where we actually see and interpret the image as clear or blurry.
In hyperopia, the cornea is to flat or the eye is to short and the image focuses behind the retina as show by the book all the way to the right in the picture. Your optic nerve transmits the book in the middle to your brain, and it interprets it as blurry.