Just as the name implies, offscreen images are images that appear below the fold. Since users can't see offscreen images when they load a page, there's no reason to download the offscreen images as part of the initial page load.
Full article
Offscreen Loading
Just as the name implies, offscreen images are images that appear below the fold. Since users can't see offscreen images when they load a page, there's no reason to download the offscreen images as part of the initial page load.
Full article