Answer:
20/20 vision is a term used to express normal visual acuity (the clarity or sharpness of vision) measured at a distance of 20 feet. If you have 20/20 vision, you can see clearly at 20 feet what should normally be seen at that distance.
Explanation:
First, it's important to note that the “20” refers to 20 feet, which is the distance from which the optician checks your visual acuity. This is based on American practice, while in the UK we tend to go by 6 metres. If you ever hear 20/20 vision being referred to as 6/6 vision, it means the same thing.