Understanding Spring MVC redirect prefix

I'm updating Spring MVC knowledge. When i come to Spring return types. There's some impediments that make me confuse. In this documentation: Mapping Requests With @RequestMapping they return appointments/newand redirect:/appointments. What's is the main difference between these two return type ? As i'm understanding the first type return as a forward action, but if i'm right, why they also publish forward:/ as a return type ?