It can display images in your terminal. This is made pretty clear by the first paragraph on the page and also by the Wikipedia article it links to[0]; I'm wondering what else you're asking for.
I haven't really tried sixel yet but I run wezterm as a daily driver and it is very convenient to be able to view images in the command line. e.g ls the directory and then run img foo.jpg on the images in the directory without needing to switch windows.
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[ 0.16 ms ] story [ 50.3 ms ] thread[0]: https://en.wikipedia.org/wiki/Sixel