At one point while your eye was closed, the circle to the side disappeared. what is that point called? why did it happen? what parts of the eye are involved with the inability to see? how do these eye parts function? what is a practical way you can use this knowledge of not being able to see objects at a certain point?

I'm rather confused about your question, but I believe you are referring to a blind spot caused by your optic nerve. The optic nerve runs from your retina to your brain, it sends all the visual information that your retina picks up. Because this nerve does not have any cones or rods on it, like your retina does, you cannot see with this part of your eye. By positioning an object correctly and looking at something at the right angle, the object can seem to disappear. Your brain usually just imagines a picture in this blind spot, so as to fill in the gap.