C ++构建系统（编译器）没有什么区别，约定。

The C++ build system (compiler) knows no difference, so it's all one of conventions.

约定是.h文件是声明，而.cpp文件是定义。

The convention is that .h files are declarations, and .cpp files are definitions.

为什么.h文件是#included - 我们包括声明。

That's why .h files are #included -- we include the declarations.