Ajax applications have a few major differences from typical web apps. First, any web page can communicate with the server at any time, and not just by submitting forms and following links. Second, you can update any part of a page at any time. Users get a more responsive site with immediate feedback. Even though using Ajax techniques usually requires significantly more sophisticated design and implementation skills, the benefits to the end user are so great that Ajax-enabled web applications are becoming the rule, not the exception. Fortunately, Rails makes Ajax so simple that, for typical cases, using Ajax is almost as easy as not using it.
Rails has a simple, consistent model for how it implements Ajax operations. Once the browser renders the initial web page, different user actions cause it to display a new web page (like any traditional web application) or trigger an Ajax operation:
This trigger could be the user clicking on a button or link, ...