如何分辨定义和声明

extern "C" { type __declspec(dllexport) name; }

Note: The braces ({}) are required. If you omit them, this becomes a declaration, not a definition.
即为什么认为 extern "C" { type __declspec(dllexport) name; } 为定义
而extern "C" type __declspec(dllexport) name; 为声明呢？