Cataract is a clouding of the natural crystalline lens within the eye which reduces the quality of vision. Correction involves surgery to replace the lens when visual function is compromised sufficiently.
A cataract is opacification of the natural lens of the eye. Just like a camera, the eye has a lens which focusses light onto the retina (camera film of the eye). This lens opacifies with age as well as medical conditions, medications and other less common interventions such as radiotherapy. Treatment is only required when visual function limits daily activities sufficiently to warrant surgery to replace the lens of the eye. Cataract surgery involves replacing the natural lens of the eye. This procedure is very common and highly successful being performed most commonly in the day surgery setting under local anaesthetic.
Changing the lens will change the refraction (power) as well as the astigmatism (curvature of refracting surface) of the eye, meaning glasses prescription will often change after surgery. You will need to discuss with your surgeon refractive outcomes such as short and long sight and the options for glasses independence if this is important to you.