AJAX is used to update a part of a web page, without reloading the entire page. This is an essential feature when the user needs fast results without waiting for the HTTP response. AJAX can be used where small amounts of data need to be retrieved from the server without reloading the entire page. Few of the use cases of AJAX are data validation without submitting the form and dynamic dropdown population based on other input values. Using AJAX can save bandwidth and reduce the load on the server.