Bootstrap popover is not working

Although the accepted answer is fine, when dealing with popovers, please be careful of situations with double initialization as well (Fiddle example). The below JavaScript will fail.

<br/>
<br/>
<a href="#" id="firstButton" class="btn btn-primary" rel="popover" data-message="Message">Click Me (Working)</a>
<br/>
<br/>
<a href="#" id="secondButton" class="btn btn-primary" rel="popover" data-message="Message">Click Me (Failing)</a>

If you double-initialize and your popover uses values that may change or custom content, etc., you will be in a world of hurt:

$(function () {
    $('#firstButton').popover({
      container: "body",
      html: true,
      content: function () {
        return '<div class="popover-message">' + $(this).data("message") + '</div>';
      }
    });
    $('#secondButton').popover(); // <-- The first initializer does this, which causes the next one to fail on the next line.
    $('#secondButton').popover({
      container: "body",
      html: true,
      content: function () {
        return '<div class="popover-message">' + $(this).data("message") + '</div>';
      }
    });
});

From the Docs on Popovers:

Opt-in functionality:
For performance reasons, the Tooltip and Popover data-apis are opt-in, meaning you must initialize them yourself.

So you must call .popover() manually in JavaScript like this:

$("[data-toggle=popover]").popover();

Or you can use whatever selector you want

Here's an example using StackSnippets.

$("[data-toggle=popover]").popover();

body {
  padding: 50px;
}

<link href="//maxcdn.bootstrapcdn.com/bootstrap/3.2.0/css/bootstrap.min.css" rel="stylesheet"/>

<script src="https://ajax.googleapis.com/ajax/libs/jquery/1.11.1/jquery.min.js"></script>
<script src="//maxcdn.bootstrapcdn.com/bootstrap/3.2.0/js/bootstrap.min.js"></script>


<button type="button" class="btn btn-lg btn-danger" 
        data-toggle="popover" title="Popover title" 
        data-content="And here's some amazing content. It's very engaging. Right?">
  Click to toggle popover
</button>

Note: This is similar to the answer to Bootstrap Tooltip Not Showing Up