How do i use "Heap" properly and why to use it?

#include<iostream> /// I still don't understand how and why to use heap...
#include<cstdlib>
#include<cstdio>
using namespace std;
int reference_lol(void);

int main()
{
    cout << "Heap, Pointers" << endl;
    int v1 = 15;
    int* v1p = &v1;
    cout << "v1 = " << v1 << ", v1 address is: " << v1p << endl;
    int& v1r = v1;
    cout << "Insert a value for v1: " << endl;
    cin >> v1r;
    cout << "v1 = " << v1 << ", v1 address is: " << v1p << endl;
    const int holder = v1;
    const int* holderAddress = &holder;
    cout << "holder = " << holder << ", holder address is: " << holderAddress << endl;
    int newHolder = holder;
    int* const newHolderAddress = &newHolder;
    cout << "newHolder = " << newHolder << ", newHolderAddress address is: " << newHolderAddress << endl;
    cout << "Enter a new value " << endl;
    cin >> *newHolderAddress;
    cout << "newHolder = " << newHolder << ", newHolderAddress address is: " << newHolderAddress << endl;
    cout << "Enter new value: " << endl;
    int myNewPointer = reference_lol();
    cout << "Successful" << endl;
    cout << "Final: " << myNewPointer;

    return 0;
}
int reference_lol(void)
{
    int lastVariable;
    int* lastVariableAddress = new int(lastVariable);
    cout << "lastVariable =  " << lastVariable << ", lastVariableAddress address is: " << lastVariableAddress << endl;
    cout << "Enter new value: " << endl;
    cin >> *lastVariableAddress;
    cout << "lastVariable =  " << lastVariable << ", lastVariableAddress address is: " << lastVariableAddress << endl;
    return *lastVariableAddress;
delete lastVariableAddress;

}