title: Rails 4 - Many to many relationship
body: <p>I have a <code>Bookmark</code> model. I would like to have a <code>List</code> model. So my users can create Bookmark lists.</p>
  
  <p>I've created a <code>List</code> scaffold with this command</p>
  
  <pre><code>rails generate scaffold List title:string
  </code></pre>
  
  <ol>
  <li>A List can have many bookmarks</li>
  <li>A Bookmark can have many lists</li>
  </ol>
  
  <p>Can someone help me to create List Bookmark relationship.? </p>
  
  <p>It would be awesome if you can give me some resources to learn. </p>
  
  <h2>Update:</h2>
  
  <blockquote>
    <ol start="2">
    <li>A Bookmark can have many lists</li>
    </ol>
  </blockquote>
  
  <p>Lets say I bookmarked <code>http://stackoverflow.com</code>. And say I have two lists like:</p>
  
  <ol>
  <li>Programming Help</li>
  <li>Favorite sites</li>
  </ol>
  
  <p>Then I should be able to add my bookmark to both lists.</p>
  
  <p>So I guess <code>A Bookmark can have many lists</code> is a valid statement.</p>