AJAX is asynchronous JavaScript and XML. A technology that can be considered relatively new. With it, the utility will not reload completely. The missing/new information is loaded to update the information. This greatly speeds up the work and simplifies it.

AJAX is mainly used in interactive user interfaces. Data exchange “browser-server” occurs in the background. We can describe the process as follows:

The user opens a page on the Internet.
Interaction with one or another element takes place.
The JS script determines what data is needed to update the page.
The browser sends a corresponding request to the web server.
The latter is responsible for returning the document to which the request was sent.
The script corrects the page taking into account the received data.
In general, the principle of operation is based on two variants. Each has its own nuances.

After the application of these technologies is functioning without reloading the entire page. This is a relatively quick solution to the problem.

The second approach – using DHTML for dynamic adjustment of information on the page.

What includes AJAX
When drawing up the code of the utility and the study of materials on the principles of web software need to understand – AJAX is not an independent technology. It includes the following implementation methods:

• HTML and CSS – to serve and style electronic materials;
• DOM-models – in charge of dynamically displaying and interacting with relevant information via JS;
• XMLHttpRequest or other transports (Iframe, SCRIPT tags and so on) – asynchronous exchange of content with the web server;
• JSON or other format of the corresponding nature (formatted HTML, test “variations”, XML) – exchange of information.
• In fact, AJAX – the concept of applying several technologies at once server-side.