Refraction is the scientific term for the bending of light as it travels through one object to another. Vision happens when light rays are bent or refracted as they travel via the cornea and the lens. Light is trained on the retina, which converts the light-rays into signals that are sent to the brain via the optic nerve. The brain then translates these signals into the images we see.
A refractive error is one of the most common eye disorders. It means that the eye's shape does not bend light correctly so that it cannot focus on the right area of the retina. This results in blurred or unfocused images.