It is a function, you have a declaration:
TVec createTVec(); // factory function
so it might look like:
TVec createTVec() {
TVec ret;
// initialize it
return ret;
}
What does vt = createTVec();
it assigns result from createTVec() function to vt variable.
In C++98 this function will return vector using temporary, since C++11 move semantics will be used. But, actually compiler might (and probably will) in such case do (N)RVO - Return Value Optimization.