ECMAScript (shortened as ES) is the standardized specification of the scripting language used by JavaScript, as well as less known languages JScript and ActionScript.
The versioning convention of ECMAScript has been the subject of hot debates. We often refer to ES5 (understood by most browsers), ES6 (the future of JavaScript) and even ES7 (the far future of JavaScript), but the official appelation for ES6 would actually be ES2015. The intention is to publish a version of the specification a year, making the language evolve quicker than ever. Still, most developers use ES5 and ES6 terms.