Server-side authentication using App Tokens is an alternative way to
authenticate to the Box API with fixed, long-lived Access Tokens that are
restricted to the application’s Service Account. App Token Auth is
intended to be used by applications leveraging Box View.
A server-side App Token is an authentication method where the application only
has access to read and write data to its own account. By using this
authentication method there is no need to authorize a user as the application is
automatically authenticated as the Service Account that belongs to that
application.