Ajax
Technology utilized to send data in an asynchronous way, where you can send and receive more than one information at a time from the server and where the page doesn't have to reloaded for this.
Example 01: receving comments and likes on Facebook photos/comments without having to reload the page for them to be shown.
Example 02: Google Maps, where only by dragging the image it will load new content, without loading up the page each time.
Examples
Synchronous and Asynchronous JS, Event Loop, Promises, APIs, Fetch, Try and Catch statments
HTTP
Hypertext Transfer Protocol
XMLHttpRequest
The object XMLHttpRequest.