What sort of disorder is farsightedness?

Can't see near. Farsighted eyes are focused far off into the distance. They tend to be small eyes that cannot bring near images into focus on the film layer of the eye (retina). The images would essentially form behind the eye, and one would have to walk backwards to bring the retina to the image. Glasses correct farsightedness by providing extra focus to "bring" the image forward onto the retina.
A refractive error. A "farsighted" person has an eye too short for the optics. This means their cornea + lens cannot bend the light enough to focus on a point on the back of the eye. To correct this, they need eyeglasses which assist in light bending, a type of magnifying glass. The eyeglass of a farsighted person will focus light to a point (a myopes glasses spreads the light).