When you successfully run expo publish for your project, a project page is created that shows your app icon and description,
and includes a QR code that can be scanned to open the app in some situations.
The Expo client app for Android can open any app, but due to limitations of the iOS platform, you are only able to view your own projects or projects published to a development team that you are a member of. This is useful in testing and ongoing development work, but rather than sharing your project page to end-users you should deploy to app stores.