<utility>
Defines Standard Template Library (STL) types, functions, and operators that help to construct and manage pairs of objects, which are useful whenever two objects need to be treated as if they were one.
For a list of all members of this header, see <utility> Members.
#include <utility>
Remarks
Pairs are widely used in the Standard C++ Library. They are required both as the arguments and return values for various functions and as element types for containers such as map class and multimap class. The <utility> header is automatically included by <map> to assist in managing their key/value pair type elements.
See Also
Reference
Thread Safety in the Standard C++ Library