I can't figure out why the Unresolved reference: webView error occurs?

Question

Kotlin

I started to study kotlin, I had to quickly make a WebView application, I found a ready-made code I created a kotlin project on android studio, I paste this code and the Unresolved reference: webView error comes out

Answer 1

The webView variable is not declared. Read the textbook or something, these are the most basic basics