What is the std::swap function in C++?

template<class T>
constexpr void swap(T& a, T& b); // Swap the values a and b
template< class T2, std::size_t N >
constexpr void swap( T2 (&a)[N], T2 (&b)[N]); // Swaps the arrays a and b.

// The following header file needs to be included to use std::swap()
#include <utility>
#include <iostream>
using namespace std;
int main() {
  int a = 10, b = 5;
  
  // before
  std::cout << "a: " << a << "\tb: " << b << '\n';
  swap(a, b);
  // after
  std::cout << "a: " << a << "\tb: " << b << '\n';
}

// The following header file needs to be included to use std::swap()
#include <utility>
#include <iostream>
using namespace std;
int main() {
  int even[] = {2, 4, 6, 8, 10};
  int odd[] = {1, 3, 5, 7, 9};
  
  // before
  std::cout << "odd: ";
  for(int x: odd) {
    std::cout << x << ' ';
  }
  std::cout << '\n';
  std::cout << "even: ";
  for(int x: even) {
    std::cout << x << ' ';
  }
  std::cout << "\n\n";
  // swapping arrays odd and even
  swap(odd, even);
  // after
  std::cout << "odd: ";
  for(int x: odd) {
    std::cout << x << ' ';
  }
  std::cout << '\n';
  std::cout << "even: ";
  for(int x: even) {
    std::cout << x << ' ';
  }
  std::cout << '\n';
}