What does the variable spatial_size mean?

[jsuyanyong]

I don't understand the mean of the variable spatial_size defined in find_car.py and svc_save.py, I find it is used as parameter size in function bin_spatial(), and what does the variable spatial_size and features returned in below function mean? Thank you! @windowsub0406

def bin_spatial(img, size=(32, 32)):
    """ Define a function to compute binned color features   """
    # Use cv2.resize().ravel() to create the feature vector
    features = cv2.resize(img, size).ravel()
    # Return the feature vector
    return features