Subdivision surfaces are piecewise parametric surfaces defined over meshes of arbitrary topology.
It's an algorithm that maps from a surface to another more refined surface, where the surface is described as a set of points and a set of polygons with vertices at those points. The resulting surface will always consist of a mesh of quadrilaterals.
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It would help to use the last frame as your video thumbnail, with all the calculation steps visible. Show the viewer what they're getting from their time investment, before they even click on the link.
Also the presentation seems pretty dry. The introduction is particularly difficult to sit through. It seems a poor use of the video medium, to lay out a bunch of concepts, but show only a subdivided rotating cube, whose rotation doesn't even loop. It would be much more engaging to show brief visual examples of each point as you introduce them.
Even better, visually show an overview of the 11 hours of content, what is the viewer expected to gain from their investment?
You can find a much better overview in the trailer video: