This node takes multiple vectors representing the points of a polygon and computes the normal of that polygon. At least 3 points are needed to compute the normal. If more than 3 non-coplanar points were input, the computed normal will be the average of the normals of each 3 points. If the points are collinear, the node will return a zero vector because no normal can be computed.
The order of points matter, because the cross product is used to compute the normals. So, reversing the order of points reverse the direction of the normal.