the capability to be updated as the user interacts with it. AJAX is
described as asynchronous because it allows data to be exchanged with the
server and parts of the page updated dynamically without delay to the user
experience or the need to reload the entire page.
The philosophy behind AJAX is to load the static parts of a webpage once, updating the dynamic parts (i.e. those bits which can change) as necessary without needing to reload anything unnecessary (such as the static parts of the page). This makes small updates much faster, because the majority of the page is unchanged and does not need to be reloaded. As well as a quicker user experience, AJAX also reduces the amount of data that needs to be downloaded from the server to the client, reducing bandwidth and potentially also processing requirements.
There is some dispute over whether or not the name should be capitalised, i.e. AJAX or Ajax. The argument in favor of not capitalizing the name is that Ajax stands for an approach rather than an acronym.
For more information see: