title: What is the difference between a vector and a matrix in MATLAB?
body: <p>I've seen the following statements in a help file:</p>
  
  <pre><code>xL = [-6 -6];
  xU = [6 6];
  </code></pre>
  
  <p>I didn't understand whether <code>xL</code> and <code>xU</code> are vectors or matrices. Thank you.</p>