When the user enters your application, vue-router will try to match paths to the one that the user is trying to access. If there is a property called alias in the route object, this property will be used by the vue-router to maintain the old route under the hood and use the alias route instead. If an alias is found, the component of that alias is rendered, and the router remains as the alias, not showing the user the change, making it transparent.
In our scenario, we made a transformation for our application to now handle all the users called on the /user namespace, but still maintaining the old URL structure so that if an old visitor tries to access the website, they will be able to use the application normally.