Basically what happens in this line
std::vector<cv::point xmlns:cv="#unknown">* ptPtr = (std::vector<cv::point>*)param;</cv::point></cv::point>
is that the input argument
param is being type cast into a pointer of type
std::vector<cv::Point>
Then the coordinates (x,y) is added to the array/vector.
Here you can read more about
std::vector[
^]