[[POPUP_THIS:width|height|scroll(0 or 1)|from iframe(true or false)|link text]]

The sample below creates a link which when clicked opens the current page in new 300×135 popup window. This  link shortcode is mainly for expanding iframes from within the iframe’s parent window.

[[POPUP_THIS:300|135|0|true|Open this iframe in New window]]

Sends a popup flag to the page via querystring (&popup=true); so that the page know that it is now running inside a popup and may behave accordingly with respect to its parent window.. Examples may be that the popup may be programmed to close itself and refresh the parent window automatically if a form is submitted.

see also: HTML Iframes – w3schools.com