I see it here but I can't find the download option on my desktop.
Do you have multiple windows open? Or a modified (size changed) window you're using? That looks like what you're showing.
<geek speak, sort of>
Works like an app. Isn't an app. PWA is it's technical name—Progressive Web App—but it isn't an app, so to speak.
A quick answer to the difference is an app like Weather takes up space on your phone, the PWA doesn't.
In your browsers address bar, on the far right, is another option for downloads.
Resources~ It's about the same thing as the media gallery where members here can upload images, videos, and such. The Resources options are geared in a different direction. I've seen it used for downloading tutorials, a variety of downloads people can use, etc. IE: I know a guy who sells a variety of add-ons like an article management system and a showcase where members can buy/sell, etc. He also just so happens to sell Sportsbook and Pickem packages.
If I wanted to buy the showcase my download would be found on his resources page.
I have only glanced at the set up for Resources. I don't know what options it contains. An early thought was using it as a database for resources. As example would be a quick jump to every season schedule and results for the Tide. We'll see.