Description :
Returns a reference to the last element in the vector
Example :
// Initialize int vector
std::vector<int> myVector = {1, 2, 3, 4, 5};
// Save reference to the last element
int& lastEle = myVector.back();
// Last element is 5
std::cout << myVector.back() << " ";
// Change the last element by changing the reference variable lastEle
lastEle = 10;
// Last element is 10
std::cout << myVector.back() << " ";