Before I can understand what EWWW IO does, I need to understand what happens to images in Wordpress.

I'm not a Web Developer but I know enough to get me through. Despite my knowledge I'm not quite sure how WordPress serves images.

Given that I know that Wordpress, your theme or your plugins automatically creates other copies of your image at other pixels dimensions respecting your aspect ratio.

My basic understanding is this.

1. When a device loads your page, Wordpress dynamically serves the image closest in size to the container of that image. If the served image is not quite the right size the Web Browser resizes the image.
2. Wordpress picks the image closest in size to the required container, and then resizes the image dynamically to fit its container.

In other words, I don't have a clue.

What I need to understand is why Browser Resizing takes place at all.