What is an AVIF file?
AVIF is a modern image format that makes very small files. Support is growing, but it isn't everywhere yet.
AVIF, WEBP or JPG?
AVIF is usually smallest, then WEBP, then JPG. JPG still opens in more places than either.
Why it's slower
Making AVIF files takes more computing power, which is why it's used less for everyday saving.