title: Formal description of PDA
body: <p>I remember how to do a formal description of an FSM, but doing one for a PDA looks a little different. Can anyone help explain the circled part? I normally take good notes, but can't seem to find anything on this in my notebook or anywhere else. Any help is appreciated.
  <img src="https://i.stack.imgur.com/LEUGs.jpg" alt="enter image description here"></p>