A family of Microsoft word processing software products for creating web, email, and print documents.
"Outside" means on the right of a right-hand (odd-numbered) page and on the left of a left-hand (even-numbered) page. You may want to use this if you have a mirror margin setup.
In other words, if editing moves the table to a new page, "Outside" (or "Inside") will move the table to the opposite page edge or margin etc.