Not much. It's just visually separated into it's own "app". I haven't used the feature in mint but maybe you also miss out on any extensions you have installed in your browser. Maybe it'll look a little less like a browser along the top.

I use a similar feature at my job through windows/edge and it's just so I can treat this one thing like it's own application. In that case it has it's own icon on the taskbar, which i have pinned so I can open it quickly, the browser UI is gone, it's just the web page in the window, I can get to it without looking through tabs, and it allows me to do whatever in the browser (like close it entirely) without affecting this window.

as /u/Bongles says, its mostly a visual thing. Have an icon on the taskbar so it opens up 8 to that page and is separate.