Sometimes you need to display HTML without a browser interpreting it, so that you can explain how to write the HTML. For example, the details of making a link to Williams College, could be displayed like this:
<a href="http://www.williams.edu/">Williams College</a>
instead of this: Williams College.
To do this, go to your page/post editor (text mode) and place the HTML you want to display, uninterpreted, inside a begin and end code tag, like this:
You can place another shortcode between the being/end code tags ([code][/code]) to display the shortcode without it being interpreted.