Dynamic web pages began with the invention of the scripting language JavaScript. JavaScript support in major web browsers meant that web pages could incorporate more meaningful real-time interactions. For example, if you’ve filled out an online form and hit the “submit” button, the web page can use JavaScript to check your entries in real-time and alert you almost instantly if you had filled out the form incorrectly.
But the dynamic web as we know it today truly came to life when XHR (XMLHttpRequest) was introduced into JavaScript, and first used in web applications like Microsoft Outlook for the Web, Gmail and Google Maps. XHR enabled individual parts of a web page ”” a game, a map, a video, a little survey ”” to be altered without needing to reload the entire page. As a result, web apps are faster and more responsive. (definition courtesy of Google Chrome’s “20 Things I Learned About Browsers and the Web”)
