You are familiar with HTML.
You know basic image formats like jpg, png and svg.
You are somewhat familiar with CSS and enough have enough expertise to read, understand and implement the MDN documentation.
The web is evolving, fast. Nice to have features have become something you as a developer, are expected to be familiar with here are some that are common:
Front End Routing.
Responsive web design.
Front End User Authentication.
Page Speed Optimization.
The HTML5 spec, is intended to serve a mobile web, you can think of it as two things a set of HTML tags, and several new APIs
Let us revise some new tags and attributes one by one, after that I will add an example that uses all of these.