How to use ajax in jquery to retrieve information from a database?

Hi, I would like to retrieve information from my database using ajax in jquery.  I googled this but I have not found a tutorial for exactly what I am trying to do.  (also, many of them had asp.net or C# in them, which I am not familiar with yet)

I know how I would normally retrieve info from the database with php:  (example)

      $query = "SELECT name FROM submenus WHERE id=" . $id;
      $result = mysql_query($query, $conn);
      confirm_query($result);
    while ($row = mysql_fetch_assoc($result)){
                        $name = $row['name'];
    }

but if you want this to change each time according to an item being clicked the page would have to reload.  I would like to display information (details) next to an image (according to the image that is clicked) without the page reloading.

Can anyone tell me a real SIMPLE way of retrieving data from a database or know of a good tutorial for this (jquery/ajax/php)?