What is the meaning of Pop-up?

Coming into view suddenly from a concealed position.

Opening out to form a three-dimensional structure when the page of a book is opened.

Operating or existing for a brief period only; temporary.

Employing the cold launch technique.

A pop-up advertisement; an advertisement that is triggered to appear on a computer screen when the user accesses a particular web page.

A pop-up ball: a ball that has been hit to a considerable height above the infield or the shallow outfield; a pop fly.

A folded paper element which pops up from a book, greeting card, etc.

A business that opens for a brief temporary period only, such as a temporary restaurant.

pop-up advertisement

pop-up (folded paper element which pops up from a book)

pop-up (opening out to form a three-dimensional structure when the page of a book is opened)

Source: wiktionary.org