Yeah,it's basically the fact that your ears pick up a mix of your voice both from inside your bpdy as well as when it gets outside of your mouth,that's why since what you record is only what goes outside,and not picked from inside,it sounds different.

By the way.did you guys realise that your image of how you look is exactly the opposite of how you really look?
Here's why:
The image you have in your head of yourself is what you see when you look in the mirror,but of course this is a mirror image of yourself.How you really look like is how you look like in a photo.That's how people see you,not how you see yourself in the mirror.
You'll notice this if you have a scar on the face,or a gap in your teeth or something;when you look at a photo(especially if you haven't had one taken in a while),it tends to throw you off sort of,you just have this feeling it looks different,but you can'y quite point out what it is.
That's what it is.