Remember your High School Geometry?
Remember lines? How they extend in both directions unendingly? They have length, but no width. What sort of thing is a line? What do you suppose an infinitely long line is like? Does it make sense to think or talk about an infinite line?
Now think about circles. What sort of a thing is a circle? What does it look like? If all circles look the same, how big could a circle be and still be considered a circle? What might a circle of infinite circumference look like?
Do you think you see a relationship between these two things? What is the image above a picture of?