Plugin convert PNG to WEBP

Hello.
I have installed the GRAV plugin which converts graphics to PNG format:
https://github.com/greenrivers/grav-plugin-webp
As it looks, it also converts all my images on the website. But on my site the PNG images are still delivered.
Can the plugin convert the images and deliver them as WEBP, and alternatively, if the browser can't display WEBP, deliver the PNG?
Or have I misunderstood the plugin?

If i read the plugin you must clear cache after do converts

After conversion You must clear cache.

Btw thanks, i will use thats plugin too.

I did not understand what this plugin does now.