what is the following list of behind the scenes?

I am studing c++ , and i saw a range based for loop like this

vector and list is included

for(int i : {1,2,3,4,5})
    std::cout << i << ' ';
std::cout << std::endl;

So my question is what is the temporary {1,2,3,4,5} in the for loop behind the scenes ?