Asynchronous JavaScript and XML (Ajax) is a web development protocol that serves as a technique used to effectively send and retrieve data in the background without having to refresh a webpage.
An example of Ajax in action today would be a client opening up a social media application. In most cases, the website will automatically notify the client of new updates by other clients. Website users are able to receive this information without refreshing the page as Ajax utilizes JavaScript XMLHttpRequest Object to make HTTP requests in the background. Aside from clients not having to refresh webpages for updates, Ajax offers many other standard applications such as:
Asynchronous Messaging where clients exchange data to and from servers in the background without having to refresh the webpage.
Responses between client-server are handled through a Callback, which is a function that serves to respond to clients when the server is ready to send back information.