What is Android WebView testing and its benefits for website?

I am working on a website customisation and its almost done and tested over various devices for its working and responsiveness. But my client continuously asking for test this website on Android WebView. For this I study This Article and what I understand is that WebView is used for execute webpages over android app. Correct me if I am wrong.

The website I am talking about has no android app. So please let me know

• How do I perform Android WebView testing for this website?
• What are Android WebView testing benefits for this website, when there is no android app using its webpages?
• and why it is important to perform Android WebView testing for this website when users have fully functional web browser in their mobile ?