Sorry for the noob question, but I'm confused as to how tar update command (tar -u) works exactly.
Let's say in my home folder, I create a tar of my Documents directory named Documents.tar. Then let's say some time goes by and I create, delete, and update some new files within Documents.
If I perform 'tar -uvf Documents.tar Documents', then it will add, remove, and update files within Documents.tar accordingly?

Also on a side note, when I was looking at the update description on computerhope.com, it mentioned compatibility for "extended headers"- what are they?

Thanks for any insight!