I can't remember anyone ever going out of the way to describe sight to me; I think I just picked it up at the same time I learned about the rest of the world around me. Although I do remember it took me a while to really understand that people can't see through walls or around corners. Right up until age 7 or 8, I just assumed if I could hear someone, they could see me. Shades took me even longer to come to grips with, and I don't think I was fully comfortable with the idea that both the sun and mustard are yellow, but they aren't the same color at all, until age 11 or so. I still find the idea of perspective (far objects usually look small) odd, but it doesn't come up in my every day life, so I'm OK with that.