AJAX is a very powerful and flexible tool that allows developers to create more streamlined applications. It can be used for a wide range of purposes such as verifying login credentials or loading content. The main benefit of AJAX is that it is asynchronous; the whole page does not need to be reloaded in order for it to receive new data.
WordPress is well-equipped for AJAX, it has a great mechanism for working with it allowing you to implement AJAX functionality with little fuss. In this article I'll take you through the basics of AJAX and create a very simple extension that pulls in search results using AJAX in Twenty Fourteen.