title: What does a table with only 2 foreign keys do?
body: <p>I've researched about MySQL and I've come across this interesting ERD. I understand all of it except the <code>user_chat</code> table here. It has 2 foreign keys referencing from table <code>chat</code> and <code>user</code>. What does that do anyway? Does that mean:</p>
  
  <ol>
  <li>I have to <code>INSERT INTO message, chat, user_chat</code> on manual when there is a new chat?</li>
  <li>I can only do <code>SELECT</code> statement with this <code>user_chat</code> table?</li>
  <li>The <code>user_chat</code> cannot contain other columns like <code>favorite</code> in case people want to quickly access it?</li>
  <li>Can I delete a row in <code>user_chat</code> table, since they are not <code>unique</code>?</li>
  </ol>
  
  <p>I'm self-learning and still a beginner on this subject so it would mean a lot if this can be explained to help me understand it. Much appreciated!</p>
  
  <p><a href="https://i.stack.imgur.com/ByZ41.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/ByZ41.png" alt="enter image description here"></a></p>