From its description:
Portal is a Mac, iPad and iPhone app that uses immersive technologies to create instant escapes to some of the world's most beautiful places.
If you work on something and need to focus, noise around can break your concentration. You can use headphones, but then you need certain kinds of music, which also can break your focus if it suddenly changes.
Portal creates sounds of nature that are both beautiful and stable. The good thing about it is that it is suitable for both work and leisure. If you travel on a bus or a plane and you want to relax and tune away from the surrounding noise, Portal will help.
Portal app has several interesting features. Desktop app can show beautiful videos as desktop wallpaper, temporarily replacing your wallpaper. Both desktop and iOS app can mix its sounds into your music, which you play in other apps. This creates an interesting effect like listening to music in the forest.
iOS app is also greatly designed and beautiful.