AJAX stands for Asynchronous JavaScript And XML (though we usually use JSON now!). It lets you: - Load data from a server without refreshing the page - Send data to a server in the background - Update parts of a page dynamically Think of it like this: Instead of reloading the entire web page when you need new data, AJAX lets you fetch just the data you need and update only the parts that changed. Real-world examples: - Loading new posts as you scroll (infinite scroll) - Searching without page reload (autocomplete) - Submitting forms without page refresh