Maybe I'm not the target audience, but this website gave me absolutely no idea what this app is. Is it some streaming music stations?

It is. Go to https://poolside.fm . They are a “retro” webradio with a summery vibe.

The original site: https://poolside.fm/

Zero information, just a link to the App Store. Pass.

edit: the App Store didn’t have any information either, no idea what this app is

This is a gorgeous site, to not even mention the app it’s marketing.