Custom Elements v1 - Reusable Web Components
Custom elements allow web developers to define new HTML tags, extend existing ones, and create reusable web components.
Shadow DOM v1 - Self-Contained Web Components
Shadow DOM allows web developers to create compartmentalized DOM and CSS for web components
HTML Imports
Include for web
Shadow DOM 301
Advanced concepts & DOM APIs
Shadow DOM 201
CSS and styling
HTML's New Template Tag
Standardizing client-side templating