<input type="checkbox">

<input> is a part of the native HTML language.

• Methods
• Style
• Behavior
• A11Y

<nifty>Foo</nifty>

Not part of the language
 

• HTMLUnknownElement

<my-thingy></my-thingy>

Custom Elements are a way for us to invent/include 'slang'.

• dasherized
• like new words in a dictionary, explained in terms already understood.

Let's play...
https://codepen.io

https://cdnjs.cloudflare.com/ajax/libs/document-register-element/1.1.1/document-register-element.js

Her pens are things of  legend...

Ana figures out cool stuff
and then teaches the rest of us...

So Ana explained...

I want to use that!