# Point travels around curve

I wonder what does this mean: Point travels around curve. I try to figure out some math explanation in the book and I can't move forward because I can't understand these words.

I can understand when point intersect curve (i.e. lie on it). I can understand when curve envelopes around point(e.g. the center of circle, ellipse). But what doses that mean when Point travels around curve ? Could you please describe this process in more details?

P.S. If that help this is slice from the book:

A third rule is the nonzero winding rule. The winding number of a point P with respect to a curve C that does not contain the point is defined as follows. Consider a point Q that travels once around C. The endpoint of a vector from P to Q, after normalization, travels along the unit circle centered at P. If we imagine the track of this endpoint as a rubber band, and let the band contract, it will end up wrapped about the circle some number of times. The winding number is the number of wraps (for clockwise wraps, the winding number is negative).

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It means it's a moving point; not simply a point. –  Michael Hardy Jan 25 '12 at 21:08
Moving where and how regarding the curve? –  Michael Z Jan 25 '12 at 21:41

They don't literally mean that the curve is somehow flowing at all. Imagine instead that the curve is a track, and an object is on top of that track and is traveling around it.

So in the case of a circle, say, then we might imagine a circular rail or something and a car on that rail. The path of that car once around the curve will be that circle, once around. (And the winding number for anything inside the circle would be 1, and 0 for everything outside the circle).

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