I don’t know what a .webp file is but I don’t like it. They’re like a filthy prank version of the image/gif you’re looking for. They make you jump through all these hoops to find the original versions of the files that you can actually do anything with.
It’s a newer image file format. You could think of it as a “better” version of a GIF or PNG. It compresses to a smaller file size with better quality, so lots of sites are using it now to speed up image loading without sacrificing quality.