In previous lessons we covered important parts of HTML and also much of the Styling world (CSS, SCSS...).
What can you do with it?
These days you can build full-blown web or mobile apps as well as real time networking applications like chats, video streaming services, command-line tools or even games.
The first version of ECMAScript was released in 1997, then starting from 2015 ECMA has been working on annual releases of a newest specification. In 2015 they released the ECMAScript (or ES to simplify) 2015 -> ES2015, which is also called ECMAScript 6 or ES6 for short.