在用C\ c++编写的代码上下文中，无序执行与有序执行之间的区别

Could anyone explain to me(in plain english) out-of-order versus in-order execution? I'm reading some theoretical texts on that and I feel that I can't quite grasp it. A small example in the context of C\C++ could be of help. What are the particularities in regards to multicore processors and multithreading?Could anyone explain to me(in plain english) ou