A variable can reference another variable using the & symbol.
string soda = "coke"; // soda variable
string &drink = soda; // reference to soda
cout << soda << "\n"; // Output: coke
cout << drink << "\n"; // Output: coke
cout << &soda << "\n"; // Output: 0x7ffed26773a8 (hexadecimal value)
cout << &drink << "\n"; // Output: 0x7ffed26773a8 (hexadecimal value)
// changing variable
soda = "pepsi";
cout << soda << "\n"; // Output: pepsi
cout << drink << "\n"; // Output: pepsi
cout << &drink << "\n"; // Output: 0x7ffed26773a8 (hexadecimal value)
cout << &soda << "\n"; // Output: 0x7ffed26773a8 (hexadecimal value)In the example above the variable drink references the variable soda. When the value of soda is updated, the value of drink also updates. That is, the drink value is whatever the food value is. &drink references the location in memory which contains the value of soda and prints as a hexadecimal value (0x7ffed26773a8) - your value will probably be different if you run the example. So both &soda and &drink map to the same memory location. Can you guess what happens if you change the value of drink?
string soda = "coke"; // soda variable
string &drink = soda; // reference to soda
drink = "sprite";
cout << soda << "\n"; // Output: sprite
cout << drink << "\n"; // Output: sprite
cout << &drink << "\n"; // Output: 0x7fffee6d3ef8 (hexadecimal value)
cout << &soda << "\n"; // Output: 0x7fffee6d3ef8 (hexadecimal value)Because &drink and &soda map to the same memory location, changing the value of one variable will also change the value of the other variable.