Yes it does render all polygons in the scene even if they are not in the direct view of the camera. This is the default setting and in most cases you want all your polygons rendered in your object to get the correct shadows, reflections, refraction ect. I do beleave you should not turn off polygons that are rendered especially if they are part of a mesh that is being deformed such as skin or clothse. You can turn on Unseen By Camera in the Object properties box for an object and the camera will not render the object in the scene, but I do not know if you can turn off the rendering of polygons in a mesh that is being deformed and still get the correct deformations. Mabye the all Knowing and all Seeing Philip can answer in more detail.
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