Here I will explain about ES5 and ES6 basic usage in Lightning Web Components
Lightning Web Components supports only to Lightning experiences and tools. It will not support in Salesforce Lightning Out so you can not use your Lightning Web components in Visualforce page directly like you are using Aura Component Lightning Out. But you can include Lightning Web Components in Aura Component then unsupported feature will support.
Create a Lightning Web Component named helloWorld, also create a Aura Component named TestComp.cmp. Now helloWorld Lightning Web Component use in side Aura Component.
Supported Experiences of Lightning Web Components
These Salesforce experiences and tools are supported.
ES6 (ECMAScript 2015)
ES7 (ECMAScript 2016)
ES8 (ECMAScript 2017)—excluding Shared Memory and Atomics