title: Thread::Join vs detach
body: <p>Why should I using <code>std::thread::join</code> and then wait until this thread has ended? I thougt the purpose of multithreading is, that I start more threads paralelly. 
  Instead of <code>join()</code>, I also could call the function "normally", like <code>foo()</code>.
  So why is their <code>join()</code>? Isn't the only thing I need <code>detach()</code>?  </p>