Looks like Google is pushing for a new graphic format for website called WebP (pronounced "weppy". /(wĕpˈē)/). It is supposed to compress a picture further with a better average of 30% reduction in size in comparison with JPEG using a lossy compression format. Since many websites employ graphics to spice up the website content as well as illustration to explain a point, having a reduced size graphic would help speed up somewhat the loading time of a website and create a better user experience. Sort of reducing the World Wide Wait for a web page or website to load up.
If you really want a website to load up double quick or triple quick even, strip everything and just leave good ol' plain text! Now we will have a really super duper fast loading website without the overheads. Perhaps we should all revert to text browser like Lynx!
In the meantime, there is no need to rush headlong to convert your current crop of JPEG photos and pictures to WebP though you could experiment with this new format on your own PC. A wait and see would be good to see whether there will be a wider adoption of this new graphic format. You will need support from all the current browsers or your website would not be usable to everybody.