c++ - What is zero overhead principle in C++? Examples?

Question

When I am reading design goals of C++11, it mentioned about zero-overhead principle without any examples or features which uses this principle. I can understand that it could be there to avoid degrading existing code performance. But,

1. Can someone explain this concept with some examples?
2. Approach they made to implement such a feature in the standard?
3. How they enforce compiler-writers to implement this?

标签： c++c++11optimizationcompiler-construction