C++11 is the name of the current version of the C++ standard, which brings many new features to the language. Qt 4.8 was the first version of Qt that started to make use of some of the new C++11 features in its API. I wrote a blog post about C++11 in Qt 4.8 before the 4.8 release which I won't repeat here. In Qt5, we make use of even more features. I will go into detail about some of them in this