Stop jQuery animation in progress.

In playing with jQuery to understand it better in a doing way, I made a project for myself to have a square move from right to left in the browser and then back again. So far I was able to make a function that does one iteration and another that resets the square but before I try to understand how to keep the loop continuously I was hoping to write code to stops the animation with another click event, but don’t know how to do that. If you can please point me where to look for clues?
Here is the code I have written so far.

.stop()

That ease Mr. Bibeault, thank you. I guess I can now move on to the hard part and write a continous loop.

Not sure why you fee that you need a loop. You can just queue up the animations.

Bear:
I got to learn new ways to think, I guess. Let me grab your book from a box (I'm in the middle of a slow move) and see how to do that. Thanks for the clues.

I tried this experiment in the file listed below. It is some progress but not at all what I expected. I can't stop it or reset it. The div hesitates before it starts.
Do you think I am on the right track? I started to read about queues to see if I need to purge something.

<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd" />
<html>
    <head>
        <title>Stat Stop Reset </title>
        <meta http-equiv="Content-Type" content="text/html; charset=UTF-8" />
        <script type="text/javascript" src="js/jquery.js"></script>
        <style type="text/css">
            body {
                background-color:#b0c4de;
                font: 12px Verdana, Arial, Helvetica
            }
            #wrapper{
                position: relative;
                margin: 0 auto;
                margin-left: 10%;
                margin-right: 10%;
                padding: .5em;
                width: 500px;
                height: 700px;
                background-color: #abcdef;
                background-color:#b0c4de;
            }
            #instruction{
                position: relative;
                margin: 0 auto;
                padding-left: 2em;
                width: 794px;
                height: 120px;
                color: black;
                background-color: #eeee88;
                border: inset 2px red;
                text-align: left;
                vertical-align: middle;
            }
            #content{
                position: absolute;
                margin-left: auto ;
                margin-right: auto ;
                top: 130px;
                left: 15px;
                /*
                margin-top: 20px;
                                padding: 20px;
                */
                width: 800px;
                height: 555px;
                background-color: #fbf2f2;
                border: inset 2px green;
            }
            #block{
                position: absolute;
                height: 50px;
                width: 50px;
                top: 150px;
                left: 25px;
                background-color: blue;
            }
        </style>
        <script type="text/javascript">
            $(document).ready(function(){
                function runIt() {
                    $('#block').animate({left: '+=620px'},2000);
                    $('#block').animate({left: '-=620px'},1000);
                    runIt();
                }
                $('#start').click(function(){
                    runIt();
                });
                $('#stop').click(function(){
                    $('#block').stop();
                });
                $('#reset').click(function(){
                    $('#block').css({top:'150px', left:'25px'});
                });
            });
        </script>
    </head>
    <body>
        <div id="wrapper">
            <div id="instruction">
                <p>
                    The first button starts the annimation
                </p>
                <p>
                    The second button stops the annimation.
                </p>
                <p>
                    The third button resets the annimation.
                </p>

</div>
            <div id="content">
                <p>
                    <button id="start">» Start Animation</button>
                </p>
                <p>
                    <button id="stop">X Stop Animation</button>
                </p>
                <p>
                    <button id="reset">O Reset O</button>
                </p>
                <div id="block">
                </div>
            </div>
        </div>
    </body>
</html>