Thanks you James and Brian for the simplified versions.
I think I've got my head around it now.
This how I've interpreted the nod.
1. Draw two concentric circles with the same number of points by using polygons.
2. Attach vectors to each point of the larger circle with direction towards the centre and length the radius of the smaller circle.
3. Rotate each vector around the point of the larger circle to which it is attached by an amount determined by several inputs.
4. Draw a curve connecting the heads of each rotated vector.

However, I don't understand fully how step 4 is achieved. In particular, what does the MoveByVec node do?
Something along the lines of 'start with the co-ordinates of point on the large circle that the vector has been rotated about and calculate the co-ordinates of a new point that corresponds with the head of the vector'?

Thanks,
Mike.