JPG vs. JPEG image formats

Question

I often use JPEG images, and I have noticed that there are two very similar file extensions: .jpg, which my mobile\'s camera and the Preview

Answer 1

No difference at all.

I personally prefer having 3 letters extensions, but you might prefer having the full name.
It's pure aestetics (personal taste), nothing else.
The format doesn't change.

You can rename the jpeg files into jpg (or vice versa) an nothing changes: they will open in your picture viewer.

By opening both a JPG and a JPEG file with an hex editor, you will notice that they share the very same heading information.