In Station, any page can be detached and used as a stand-alone window.
This comes useful when:
you have multiple screens
you want to open multiple pages side by side.
To open a page as a separate window, just hover on an app's icon and click on the "Detach" button next to the page you want to detach.
What you can't do is opening multiple instances of Station on the same computer: there can only be 1 window with the apps' dock on the left.