Ron answered your questions, but I would recommend that you don't do this.
That's one way that viruses/malware can be sent.
You get a file that looks like:
FamilyPictures.jpg
and double click on it to see the pictures.
The bad news is that since you're hiding the extension, you didn't see that the
real name of the file was:
FamilyPictures.jpg.exe
or
FamilyPictures.jpg.vbs
or anything else that can cause damage.
One of the first things I do when I see a person's pc not showing extensions is
to turn them on and explain why it's a good idea.
I wouldn't do what you want!