std::pair

template <class T1, class T2> struct pair;

This class couples together a pair of values, which may be of different types (T1 and T2). The individual values can be accessed through its public members first and second.
Pairs are a particular case of tuple.

Template Parameters

T1    Type of member first, aliased as first_type.
T2    Type of member second, aliased as second_type.

Member Variable
first        The first value in the pair
second    The second value in the pair


ref. http://www.cplusplus.com/reference/utility/pair/