ES (ECMAScript) followed by a number, references the specific version of ECMAScript, for example ES1, ES2 etc. So far there are 10 versions of ES from ES1 to ES10. ES.Next references the next upcoming version of ES.
Except for ES1 and ES2, each version of ES introduces a new set of features to the language. For example, regular expressions and try/catch exception handling were added to ES3. Whereas ES6 additions include arrow function expressions, const and let keywords, and more.
Yearly ES additions allow browser vendors and developers to implement features at a constant rate.
1. Check browser support for a specific feature
2. Transpile your code
To check browser support for a particular ES feature you may use https://www.caniuse.com. The website provides a table of browsers and their versions that support a particular feature that is searched for.