ES6 (6th Edition) aka ES2015 aka ECMAScript 2015 (European Computer Manufacturers Association).
ES Module / ES6 Module / ‘JavaScript modules’ syntax
import and export
CommonJS Module syntax
require and exports
ES6 modules are only practical from Node.js v10 onwards (released in April 2018). All mainstream browsers and Node.js from mid 2018 support ES6 modules.
jQuery Plugins
The javascript in a jQuery plugin like Bootstrap expects there to be a global jQuery variable that it can modify, for example by adding a tooltip() method.