What is the difference between two join statements in the code?

In the below code, there are two joins (of course one is commented). I would like to know what is the difference between when join is executed before the loop and when join is executed after the loop?

#include <iostream>
#include <thread>
using namespace std;

void ThreadFunction();

int main()
{
    thread ThreadFunctionObj(ThreadFunction);
    //ThreadFunctionObj.join();
    for (int j=0;j<10;++j)
    {
        cout << "\tj = " << j  << endl;
    }
    ThreadFunctionObj.join();
    return 0;
}

void ThreadFunction()
{
    for (int i=0;i<10;++i)
    {
        cout << "i = " << i  << endl;
    }
}