Swift中{response in ...}的含义

Question

我是编程和Swift的新手。我正在浏览Alamofire的文档，并在以下代码块中找到了我不理解的代码声明：responseJSON { response in。

Alamofire.request("https://httpbin.org/get").responseJSON { response in
    print("Request: \(String(describing: response.request))")   // original url request
    print("Response: \(String(describing: response.response))") // http url response
    print("Result: \(response.result)")                         // response serialization result

    if let json = response.result.value {
        print("JSON: \(json)") // serialized json response
    }

    if let data = response.data, let utf8Text = String(data: data, encoding: .utf8) {
        print("Data: \(utf8Text)") // original server data as UTF8 string
    }
}

Swift中究竟是什么意思？我理解它会发出请求并获取响应哪个正文以JSON格式返回，但我不确定{ response in的含义。