Does "Maximum image resolution" resize before saving on the site? I am building a site using Drupal 7, in which users can upload content and images.

When I set the "Maximum image resolution" (on the core image field settings) to be, for example -  800x600. 

Is that mean that the pictures will first be resized and weight reduced, and only then will be saved on my Drupal site? 

I don't want to have many pictures that weight a lot on my server. I prefer to save only the images that has been resized, in order to have more space on my server.
that setting means that you can't upload an image with max resolution of 800x600. If you upload an images with a size more than that set, it will be not imported and drupal will return an error alter.