Dereferencing a reference

I'm reading "The C++ Programming Language (4th edition)" and I ran into this:

template<class C, class Oper>
void for_all(C& c, Oper op) // assume that C is a container of pointers
{
    for (auto& x : c)
    op(∗x); // pass op() a reference to each element pointed to
}

So from what I understand, we're iterating through c and getting a reference to x, which is the current iteration. x is then passed to the function call operator of op, but it is dereferenced first? Why would x be dereferenced?