I have a wordpress website. I upload my pictures to the media library. And when I import a picture in a post, you get the options, one of which ask you what size to display it in. And doing this results in creating a new image file that is a different size, rather than wordpress using html to control the size of the image.

The following image shows how different sized picture copies are made of the same one with different resolution.

http://imgur.com/uVqTN

Thank you everyone in advance.