Short answer:
There is no difference in semantic.
Specifically, @GetMapping is a composed annotation that acts as a shortcut for @RequestMapping(method = RequestMethod.GET).
Further reading:
RequestMapping can be used at class level:
This annotation can be used both at the class and at the method level. In most cases, at the method level applications will prefer to use one of the HTTP method specific variants @GetMapping, @PostMapping, @PutMapping, @DeleteMapping, or @PatchMapping.
while GetMapping only applies to method:
Annotation for mapping HTTP GET requests onto specific handler methods.