These are browser engines, or at least software for rendering HTML but not necessarily the actual browser. I don’t know them all, but top left, Gecko, is the engine for Mozilla, center is Web Kit for Safari, bottom center is Chromium for Chrome, Brave, Edge, etc., and bottom right is Trident, the old engine for Microsoft Internet Explorer.
There is a website that will redirect to the post on your instance but it looks like I did not bookmark it. I expect someone else will chime in with it.