References in C++, how it really works?

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I have a question about references in C++. From what I understand it's like a pointer but with a few differences. It can't be null, it can't be re-assigned and it must be initialized. Apart from this it behaves pretty much as a pointer. However I have seen some examples when I have been searching the web to find answers, that showed that references doesn't really behave as pointers after all.

In the example below I expected the reference 'n1' in the function to be 10 since it's a reference to the variable 'n1' in main. If it's a reference how can it then still be 1 even if the value is changed. It must be a copy somewhere since obviously both 1 and 10 exists at the same time. For me it acts more like a copy of the value than a reference.

#include <functional>
#include <iostream>
 
void f(int& n1, int& n2, const int& n3)
{
    std::cout << "In function: " << n1 << ' ' << n2 << ' ' << n3 << '\n';
    ++n1; // increments the copy of n1 stored in the function object
    ++n2; // increments the main()'s n2
    // ++n3; // compile error
}
 
int main()
{
    int n1 = 1, n2 = 2, n3 = 3;
    std::function<void()> bound_f = std::bind(f, n1, std::ref(n2), std::cref(n3));
    n1 = 10;
    n2 = 11;
    n3 = 12;
    std::cout << "Before function: " << n1 << ' ' << n2 << ' ' << n3 << '\n';
    bound_f();
    std::cout << "After function: " << n1 << ' ' << n2 << ' ' << n3 << '\n';
}

Output:

Before function: 10 11 12
In function: 1 11 12
After function: 10 12 12

I would be thankful if someone of you that know could help me understand what a reference in c++ really is and how it's stored in memory. (I'm not new to programming but lack some experience and knowledge in c++).

The code is taken from: http://en.cppreference.com/w/cpp/utility/functional/ref[^]

The problem is solved, I didn't realized that bind actually takes a value and therefore n1 is only a temporary variable in the function. The notation was a bit confusing though I think. Anyway thanks for all help!