Why Is the single colon In C++ Vector call, what's its function

I am trying to learn vectors; it uses confusing a ranged loop.
I Don’t understand how const int& i works in tandem with the single colon ‘:’ and vector1.

for (const int& i : vector1)
{
    cout << i << "  ";
}

>Solution :

As of C++11, this is available. It is a range-based for loop.

In your example, i is a const reference to each item in vector1 in turn.