JavaScript was originally named Mocha but was renamed LiveScript and then JavaScript. It is a lightweight, interpreted programming language designed for creating network-centric and browser-based applications. JavaScript can be used for client-side scripting through features like popup boxes and event handling, and for server-side scripting by running JavaScript code on the server with Node.js. It includes basic datatypes, operators, control flows, and built-in objects for manipulating the browser and its DOM.