The [Flask documentation shows](http://flask.pocoo.org/docs/api/#flask.Flask.add_url_rule):

```
add_url_rule(*args, **kwargs)
      Connects a URL rule. Works exactly like the route() decorator.
      If a view_func is provided it will be registered with the endpoint.

     endpoint – the endpoint for the registered URL rule. Flask itself assumes the name of the view function as endpoint

```

What exactly is meant by an "endpoint"?