title: What is the difference between Lemma and Theorem in Coq
body: <p>I can't tell in which situations I should use <code>Theorem</code> over <code>Lemma</code> or the opposite. Is there any difference (despite syntactical) between this</p>
  
  <pre><code>Theorem l : 2 = 2.
    trivial.
  Qed.
  </code></pre>
  
  <p>and this</p>
  
  <pre><code>Lemma l : 2 = 2.
    trivial.
  Qed.
  </code></pre>
  
  <p>?</p>