Not many tools support AVIF format by default and since you can occasionally download .avif pictures from Internet it makes users wonder how to convert these files to some standard format, for example JPEG, which is what avif to jpg conversion represents.
Even though Microsoft promised that Windows Paint will support AVIF format since Windows 10, it is not so, which means you have to rely on graphics editors or converters that do, for example Paint.NET or GIMP.