And emplace_back function:

Modern C++ features: in-place construction

by Arne Mertz

From the article:

Move constructors are often cheaper than copy constructors, which makes the construction and immediate relocation of objects in modern C++ more effective than in C++03. However, just moving the parts needed to construct the object in the right place can be even more effective. Several standard library functionalities use perfect forwarding to construct objects right where they are needed.